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Accepted papers to appear in an upcoming issue

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Experimental Realization of Quantum Random Number Generator with Independent Devices

Xue-bi An, Yun-Guang Han, Zhen-Qiang Yin, Wei Huang, Wei Chen, Shuang Wang, Guang-can Guo, and Zhengfu Han

Doc ID: 301041 Received 27 Jun 2017; Accepted 18 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: The generation of genuine randomness is an important task in quantum information processing and it has attracted much more attention recently. How to estimate the genuine randomness of the data generated by a given device is a central problem. T. Lunghi et al. proposed a self-testing quantum random number generator [$Phys. Rev. Lett. 114, 150501(2015)$] from a prepare-and-measure scenario with independent devices. Based on this work, Y. G. Han et al. proposed a more efficient method [$Phys. Rev. A 93, 03 32(2016)$ ] (Han16 protocol for short) to estimate the genuine randomness. We here report a proof-of-principle realization of Han16 protocol with heralding single photon source. Because all observed probabilities are exploited to bound the minimum entropy of the output data, Han16 protocol is more efficient than T. Lunghi's protocol which only uses a dimension witness value. $H_{min}\sim0.307$ minimum entropy and $1.47kbits$ quantum random numbers per second are obtained in the experiment under fair-sampling assumption with Han16 protocol. The experimental results in different levels of noise and loss demonstrate that Han16 protocol almost doubles the generation rate of quantum random number with regard to the previous protocol. In addition, the performance of our experiment shows that Han16 protocol is practical and our experimental device can tolerate loss and noise.

Dipole force free optical control and cooling of nanofiber trapped atoms

Christoffer Østfeldt, Jean-Baptiste Béguin, Freja Pedersen, Eugene Polzik, Joerg Mueller, and Jurgen Appel

Doc ID: 304575 Received 11 Aug 2017; Accepted 18 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: The evanescent field surrounding nano-scale optical waveguides offers an efficient interface between light and mesoscopic ensembles of neutral atoms. However, the thermal motion of trapped atoms, combined with the strong radial gradients of the guided light, leads to a time-modulated coupling between atoms and the light mode, thus giving rise to additional noise and motional dephasing of collective states. Here, we present a dipole force free scheme for coupling of the radial motional states, utilizing the strong intensity gradient of the guided mode and demonstrate all-optical coupling of the cesium hyperfine ground states and motional sideband transitions. We utilize this to prolong the trap lifetime of an atomic ensemble by Raman sideband cooling of the radial motion, which has not been demonstrated in nano-optical structures previously. Our work points towards full and independent control of internal and external atomic degrees of freedom using guided light modes only.

Hybrid optical pumping of K and Rb atoms in a paraffin coated vapor cell

Wenhao Li, Xiang Peng, Dmitry Budker, Arne Wickenbrock, Bo Pang, Rui Zhang, and Hong Guo

Doc ID: 305160 Received 18 Aug 2017; Accepted 18 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: Dynamic hybrid optical pumping effects with a radio-frequency-field-driven nonlinear magneto-optical rotation (RF NMOR) scheme are studied in a dual-species paraffin coated vapor cell. By pumping K atoms and probing $^{87}$Rb atoms, we achieve an intrinsic magnetic resonance linewidth of 3 Hz and the observed resonance is immune to power broadening and light-shift effects. Such operation scheme shows favorable prospects for atomic magnetometry applications.

Flat top surface plasmon polariton beams

Lauren Zundel, Rosario Martinez-Herrero, and Alejandro Manjavacas

Doc ID: 305991 Received 31 Aug 2017; Accepted 18 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: Surface plasmon polaritons (SPPs) have emerged as powerful tools for guiding and manipulating light below the diffraction limit. In this context, the availability of flat top SPP beams displaying a constant transversal profile can allow for uniform excitation and coupling scenarios, thus opening the door to developing novel applications that cannot be achieved using conventional Gaussian SPP beams. Here, we present a rigorous theoretical description of flat top SPP beams propagating along flat metal-dielectric interfaces. This is accomplished through the use of Hermite Gauss SPP modes that constitute a complete basis set for the solutions of Maxwell's equations for a metal-dielectric interface in the paraxial approximation. We provide a comprehensive analysis of the evolution of the transversal profiles of these beams as they propagate, which is complemented with the study of the width and kurtosis parameters. Our results serve to enlarge the capabilities of surface plasmon polaritons to control and manipulate light below the diffraction limit.

Precise identification of graphene layers at the air-prism interface via pseudo-Brewster angle

Chengquan Mi, Shizhen Chen, Weijie Wu, Wenshuai Zhang, Xinxing Zhou, Xiaohui Ling, Weixing Shu, Hailu Luo, and Shuangchun Wen

Doc ID: 305581 Received 25 Aug 2017; Accepted 18 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: We propose a simple method for the precise identification of graphene layers at the air-prism interface via pseudo-Brewster angle where the horizontally polarized reflection is close to zero. We find that the pseudo-Brewster angle is sensitive to the variation of graphene layers where the pseudo-Brewster angle is approximately linearly increased about 0.5 degree as the layer numbers increased. Furthermore, the sensitivity of the pseudo-Brewster angle can be greatly enhanced and reaches 0.04 degree by eliminating the influence of cross-polarization effect. Our scheme can provide a simple and effective method to identify the layer numbers of graphene.

Flat-top narrowband filters enabled by guided-mode resonance in two-level waveguides

Katsuaki Yamada, Kyu Lee, Yeong Ko, Junichi Inoue, Kenji Kintaka, Shogo Ura, and Robert Magnusson

Doc ID: 305182 Received 18 Aug 2017; Accepted 17 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: Resonant nanogratings and periodic metasurfaces express diverse spectral and polarization properties on broadside illumination by incident light. Cooperative resonance interactions may yield shaped spectra for particular applications in contrast to multilayer dielectric mirror. Here, we provide guided-mode resonance filters with flat-top spectra suitable for wavelength division multiplexing systems. Applying a single one-dimensional grating layer sandwiched by two waveguides, we theoretically achieve high-efficiency flat-top spectra in the near-infrared region. This result is obtained by inducing simultaneous nearly-degenerate resonant modes. The resonance separation under this condition controls the width of the flat-top spectrum. This means we can implement spectral widths ranging from sub-nanometer to several nanometers applying fundamentally the same device architecture.

Hybrid photonic-plasmonic near-field probe for efficient light conversion into the nanoscale hot spot

Alexander Koshelev, Keiko Munechika, and Stefano Cabrini

Doc ID: 301835 Received 01 Aug 2017; Accepted 17 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: In this Letter, we present a design and simulations of the novel hybrid photonic-plasmonic near field probe. Near-field optics is a unique imaging tool that provides optical images with resolution down to tens of nanometers. One of the main limitations of this technology is its low light sensitivity. The presented hybrid probe solves this problem by combining a campanile plasmonic probe with a photonic layer, consisting of the diffractive optic element (DOE). The DOE is designed to match the plasmonic field at the base of the campanile probe with the fiber mode. This makes it possible to optimize the size of the campanile tip to convert light efficiently into the hot spot. The simulations show that the hybrid probe is on average ~540 times more efficient compared to the conventional campanile in the 600-900 nm spectral range.

Enhanced Total Internal Reflection Using Low-Index Nanolattice Materials

Xu Zhang, Yi-An Chen, Abhijeet Bagal, and Chih-Hao Chang

Doc ID: 303972 Received 04 Aug 2017; Accepted 16 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: Low-index materials are key components in integrated photonics and can enhance index contrast and improve performance. Such materials can be constructed from porous materials, which generally lack mechanical strength and are difficult to integrate. Here we demonstrate enhanced total internal reflection (TIR) induced by integrating robust nanolattice materials with periodic architecture between high-index media. The transmission measurement from the multilayer stack illustrates a cutoff at about 60º incidence angle, indicating enhanced light trapping effect through TIR. Light propagation in the nanolattice material is simulated using rigorous coupled-wave analysis (RCWA) and transfer matrix methods, which agrees well with experimental data. The demonstration of TIR effect in this work serves as a first step towards the realization of multilayer devices with nanolattice materials as robust low-index components. These nanolattice materials can find applications in integrated photonics, antireflection coatings, photonic crystals, and low-k dielectric.

Nonlinear pulse compression stage delivering 43 W GW-class few-cycle pulses at 2 µm wavelength

Martin Gebhardt, Christian Gaida, Tobias Heuermann, Fabian Stutzki, Cesar Jauregui, Jose Antonio-Lopez, Axel Schulzgen, Rodrigo Amezcua Correa, Jens Limpert, and Andreas Tünnermann

Doc ID: 305502 Received 24 Aug 2017; Accepted 15 Sep 2017; Posted 15 Sep 2017  View: PDF

Abstract: High average power laser sources delivering intense few-cycle pulses in wavelength regions beyond the near-infrared are promising tools for driving the next generation of high-flux strong-field experiments. In this work, we report on nonlinear pulse compression to 34.4 µJ-, 2.1-cycle pulses with 1.4 GW peak power at a central wavelength of 1.82 µm and an average power of 43 W. This performance level was enabled by the combination of a high repetition rate ultrafast thulium-doped fiber laser system and a gas-filled antiresonant hollow-core fiber.

Hopping induced inversions and Pancharatnam excursions of C-points

Ruchi Rajput, B.S.Bhargava Ram, and Paramasivam Senthilkumaran

Doc ID: 305685 Received 25 Aug 2017; Accepted 14 Sep 2017; Posted 15 Sep 2017  View: PDF

Abstract: In this paper we show the acquisition of Pancharatnam phase by a C-point singularity when it is subjected to discrete cyclic polarization transformations. The SOP changes are mapped on to a Poincaré sphere as geodesical closed trajectories. Pancharatnam phase acquired by a C-point is equal to the solid angle subtended by the closed trajectories at the center of the Poincaré sphere. We show this by considering index hopping induced inversions of C-points. For example, a lemon from the North Pole of a Poincaré sphere is first converted into a star whose location can be traced to the South Pole of the Poincaré sphere and retrieved back as a lemon at theNorth Pole to complete a closed geodesical trajectory on the Poincaré sphere. Depending on the trajectory, it is shown that the lemons (stars) acquire different amount of Pancharatnam phase, which can be attributed to the amount of rotation in the SOP pattern of the lemons (stars).

Acceleratating two-dimensional infrared spectroscopywhile preserving lineshapes using GIRAF

Ipshita Bhattacharya, Jonathan Humston, Christopher Cheatum, and Mathews Jacob

Doc ID: 304846 Received 16 Aug 2017; Accepted 14 Sep 2017; Posted 15 Sep 2017  View: PDF

Abstract: We introduce a computationally efficient structuredlow rank algorithm for the reconstruction of twodimensionalinfrared (2D IR) spectroscopic data fromfew measurements. The signal is modeled as a combinationof exponential lineshapes, which are annihilatedby appropriately chosen filters. The annihilationrelations result in a low-rank constraint on a Toeplitzmatrix constructed from the signal samples, which is exploitedto recover the unknown signal samples. Quantitativeand qualitative studies on simulated and experimental2D IR data demonstrate that the algorithm outperformsdiscrete compressed sensing algorithm, bothin the uniform and non-uniform sampling settings.

Ex vivo validation of Photo-Magnetic Imaging

Alex Luk, Farouk Nouizi, Hakan Erkol, Mehmet Unlu, and Gultekin Gulsen

Doc ID: 304397 Received 08 Aug 2017; Accepted 14 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: We recently introduced a new high resolution diffuse optical imaging technique termed Photo-Magnetic Imaging (PMI), which utilizes magnetic resonance thermometry (MRT) to monitor the 3D temperature distribution induced in a medium illuminated with a near-infrared light. The spatiotemporal temperature distribution due to light absorption can be accurately estimated using a combined photon propagation and heat diffusion model. High resolution optical absorption images are then obtained by iteratively minimizing the error between the measured and modeled temperature distributions. We have previously demonstrated the feasibility of PMI with experimental studies using tissue simulating agarose phantoms. In this Letter, we present the preliminary ex vivo PMI results obtained with a chicken breast sample. Similarly to the results obtained on phantoms, the reconstructed images reveal that PMI can quantitatively resolve an inclusion with a 3 mm diameter embedded deep in a biological tissue sample with only 10% error. These encouraging results demonstrate the performance of PMI in ex vivo biological tissue and its potential for in vivo imaging.

Soliton trapping and comb self-referencing in a single microresonator with χ(2) and χ(3) nonlinearities

Xiaoxiao Xue, Xiaoping Zheng, and Andrew Weiner

Doc ID: 303628 Received 01 Aug 2017; Accepted 14 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: A shaped doublet pump pulse is proposed for simultaneous octave-spanning soliton Kerr frequency comb generation and second-harmonic conversion in a single microresonator. The temporal soliton in the cavity is trapped atop a doublet pulse pedestal, resulting in a greatly expanded soliton region compared to that with a general Gaussian pulse pump. The possibility of single-microresonator comb self-referencing in a single silicon nitride microring, which can facilitate compact on-chip optical clocks, is demonstrated via simulation.

Vertically-integrated spot-size converter in AlGaAs-GaAs

ZHONGFA LIAO, Sean Wagner, Muhammad Alam, Valery Tolstikhin, and J. Stewart Aitchison

Doc ID: 304327 Received 11 Aug 2017; Accepted 14 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: We report on the demonstration of a spot size converter (SSC) for monolithic photonic integration at a wavelength of 850 nm on a GaAs substrate. We designed and fabricated a dual waveguide AlGaAs chip. The design consists of a lower waveguide layer for efficient end-fire coupling to a single mode fiber, and an upper waveguide layer for high refractive index contrast waveguides, and a vertical SSC to connect the two waveguide layers. We measured a SSC conversion efficiency of 91% (or −0.4 dB) between the upper and lower waveguide layers for the TE mode at a wavelength of 850 nm.

Compact broadband spectrometer based on up- and down-conversion luminescence

Tao Yang, Jing-xiao Peng, Xing-ao Li, shen xiao, Xin-hui Zhou, Xiaoli Huang, Wei Huang, and Ho-Pui Ho

Doc ID: 306259 Received 01 Sep 2017; Accepted 13 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: In this letter, a compact spectrometer based on up- and down-conversion luminescence for operation in the infrared, visible and ultraviolet bands is presented. The proposed spectrometer has three components that are used for dispersion, frequency conversion and detection. The conversion component converts the incident signal beam into a spectral window appropriate for the detection component. The detection component images the speckle pattern generated by scattering or diffraction in the random structure of the dispersion component. With the 2-dimensional intensity data captured from both the speckle pattern and a calibration measurement process, one can reconstruct the spectra of the signal beam by solving a matrix equation. A smoothing simulated annealing algorithm has been implemented to improve the accuracy of the spectral reconstruction. We have analyzed possible sources of error in the algorithm and the corresponding limits of operation. The reported broadband, compact, high-resolution luminescence-based spectrometer is well suited for portable spectroscopy applications.

Field extension inside guided-mode-resonance filters under a focused beam

Antoine Bierret, Grégory Vincent, Julien Jaeck, Jean-Luc Pelouard, Riad Haidar, and Fabrice Pardo

Doc ID: 306461 Received 06 Sep 2017; Accepted 13 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: We present a theoretical study of mid-infrared guided mode resonance spectral filters made of two subwavelength metallic gratings and a dielectric waveguide, under a focused beam with a finite spot size. Study shows that, at the resonant wavelength, the lateral extension of the electromagnetic field in the waveguide is close to the width of the beam. We compare the performance of filters using gratings with a one-slit pattern and gratings with a two-slit pattern and we show that the latter gratings (biatom gratings) provide a higher transmission and a better limitation of field extension, due to an improved angular acceptance. These results open new perspectives for pixel-sized infrared filters.

Label-free brainwide visualization of senile plaque using cryo-micro-optical sectioning tomography

Yilin LUO, Anle Wang, Mengmeng Liu, Tian Lei, Xiaochuan Zhang, Zhaobing Gao, Hualiang Jiang, Hui Gong, and Jing Yuan

Doc ID: 303420 Received 01 Aug 2017; Accepted 13 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: Optical visualization of pathological changes in Alzheimer’s disease (AD) can facilitate exploration of disease mechanism and treatment. However, existing optical imaging methods have limitations on mapping pathological evolution in the whole mouse brain. Previous research indicated endogenous fluorescence contrast of senile plaques. Therefore, we develop cryo-micro-optical sectioning tomography (cryo-MOST) to capture the intrinsic fluorescence distribution of senile plaque at a micron-level resolution in the whole brain. Validation using immunofluorescence demonstrates the capacity of cryo-MOST to visualize and distinguish senile plaques with competent sensitivity and spatial resolution. Compared with imaging in room temperature, cryo-MOST provides better signal intensity and signal-to-noise ratio. Using cryo-MOST, we obtained whole-brain coronal distribution of senile plaque in a transgenic mouse without exogenous dye. Capable of label-free brainwide visualization of Alzherimer’s pathology, cryo-MOST may be potentially useful for understanding neurodegenerative disease mechanism and evaluating drug efficacy.

Tunable spin Hall effect of light with graphene at telecommunication wavelength

Xiangxing Bai, Tang long, Wenqiang Lu, Xingzhan Wei, Shuang Liu, Xiudong Sun, Yang Liu, Haofei Shi, and Yueguang Lu

Doc ID: 302389 Received 11 Aug 2017; Accepted 13 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: The Spin Hall effect of light (SHEL) has been widely studied of manipulating spin polarized photons. In the paper, we present a mechanism to electrically tune the spin shift of SHEL by means of introducing graphene layer at 1550 nm. The spin shift is quite sensitive to graphene layer near the Brewster angle for horizontal polarization incidence and can be dynamically tuned by varying the Fermi energy of graphene.We find that the position of the Brewster angle and the value of spin shift are decided by the real part and imaginary part of graphene conductivity respectively. In addition, two different tuned regions have been revealed, one is the “ step-like switch ” region where the spin shift switches between two values, and another is the “ negative modulation ” region where the spin shift declines gradually as Fermi energy increases. Those findings may provide a new paradigm for tunable spin photonic device.

Thulium-fiber-laser-pumped, high-peak-power, picosecond, mid-infrared orientation-patterned GaAs optical parametric generator and amplifier

Lin Xu, Qiang Fu, Sijing Liang, David Shepherd, David Richardson, and Shaif-Ul Alam

Doc ID: 303672 Received 31 Jul 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: We report a high-peak-power, picosecond, mid-infrared optical parametric generator (OPG) and amplifier (OPA) based on orientation-patterned GaAs (OP:GaAs) pumped by a Tm:fiber master-oscillator-power-amplifier (MOPA) employing direct diode-seeded amplification. An OPG tuning range of 2550-2940 nm (signal) and 5800-8300 nm (idler) is demonstrated with peak powers as high as 3 kW (signal) and 2 kW (idler). When seeded with a 0.6 cm-1 linewidth tunable Cr:ZnSe laser, the OPA idler linewidth is narrowed to 1.4 cm-1 and a small-signal parametric gain of 60 dB is achieved. A maximum peak power of 13.3 kW (signal) and 3.2 kW (idler) is obtained at an overall conversion efficiency of 36%.

Ultra-compact all-in-fiber-core Mach-Zehnder interferometer

Pengcheng Chen, Xuewen Shu, and Kate Sugden

Doc ID: 301535 Received 05 Jul 2017; Accepted 12 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: Optical Mach-Zehnder interferometers (MZI) are useful components in a variety of optical applications including: optical modulation; signal processing; and physical, chemical, and biological sensing. We introduce here a novel, assembly-free all-in-fiber-core MZI, which is directly written with a femtosecond laser. By introducing a positive refractive index-modified zone (PRIMZ) in half of the fiber core, the original single-moded fiber section is converted into a few-moded fiber section, where a strong coupling between the two lowest-order guided modes is generated, resulting in a well-defined interference spectrum in transmission. This device promises many significant advantages over existing approaches such as: ease of fabrication; stability; small insertion loss; robustness; extremely broad operating bandwidth, and precise and controllable cavity lengths. These advantages make this device strikingly attractive with the potential for extensive adoption in fiber communications, signal processing, sensors and laser wavelength control.

Coherent Solid-State LIDAR with Silicon Photonic Optical Phased Arrays

Christopher Poulton, Ami Yaacobi, David Cole, Matthew Byrd, Manan Raval, Diedrik Vermeulen, and Michael Watts

Doc ID: 300540 Received 22 Jun 2017; Accepted 12 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: We present the first demonstration of coherent solid-state LIDAR using optical phased arrays in a silicon photonics platform. An integrated transmitting and receiving frequency-modulated continuous-wave (FMCW) circuit was initially developed and tested to confirm on-chip ranging. Simultaneous distance and velocity measurements were performed using triangular frequency modulation. Transmitting and receiving optical phased arrays were added to the system for on-chip beam collimation and solid-state beam steering and ranging measurements using this system are shown. A cascaded optical phase shifter architecture with multiple groups was used to simplify system control and allow for a compact packaged device. This system was fabricated within a 300mm wafer CMOS-compatible platform and paves the way for disruptive low-cost and compact LIDAR on a chip technology.

Synthesis of circularly coherent sources

Massimo Santarsiero, Rosario Martinez-Herrero, David Maluenda Niubó, Juan Carlos de Sande, Gemma Piquero, and Franco Gori

Doc ID: 303522 Received 31 Jul 2017; Accepted 12 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: An experiment is presented in which a partially coherent source endowed with circular coherence is generated. The source is synthesized through a time averaging procedure, so that the mutual intensity is used as the basic correlation function. The correlation between points at different radial distances from the source center is tested by means of a Young interferometer. To confirm the perfect coherence among points along a circle concentric with the source center, the Young mask is replaced by an array of equally spaced pinholes arranged along a circle. The observed pattern is identical to that produced by the same mask, illuminated by perfectly coherent light.

Phase-locked multi-terahertz electric fieldsexceeding 13 MV/cm at 190 kHz repetition rate

Matthias Knorr, Jürgen Raab, Maximilian Tauer, Philipp Merkl, Dominik Peller, Emanuel Wittmann, Eberhard Riedle, Christoph Lange, and Rupert Huber

Doc ID: 301260 Received 06 Jul 2017; Accepted 12 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: We demonstrate a compact source of energetic and phase-locked multi-terahertz pulses at a repetition rate of 190 kHz. Difference frequency mixing of the fundamental output of an Yb:KGW amplifier with the idler of an optical parametric amplifier in GaSe and LiGaS2 crystals yields a passively phase-locked train of waveforms tunable between 12 and 42 THz. The shortest multi-terahertz pulses contain 1.8 oscillation cycles within the intensity FWHM. Pulse energies of up to 0.16 µJ and peak electric fields of 13 MV/cm are achieved. Electro-optic sampling reveals a phase stability better than 0.1 π over multiple hours combined with free CEP tunability. The scalable scheme opens the door to strong-field terahertz optics at unprecedented repetition rates.

Arbitrary-shaped Brillouin microwave photonic filter by manipulating directly-modulated pump spectrum

Wei Wei, Lilin Yi, Yves Jaouen, and Weisheng Hu

Doc ID: 305090 Received 18 Aug 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: We present a cost-effective GHz-wide arbitrary-shaped microwave photonic filter based on stimulated Brillouin scattering in fiber using directly-modulated laser (DML). After analyzing the relation between the spectral power density and the modulation current of the DML, we find the way to precisely adjust the optical spectrum of the DML thereby controlling the Brillouin gain filter spectrum arbitrarily for the first time. The manipulation of the pump spectrum consists of pre-designing the modulation current waveform and employing feedback control algorithm based on the targeted shape. The filter performance is evaluated by amplifying 500-Mbps non-return-to-zero on-off keying (NRZ-OOK) signal using a 1 GHz rectangular filter. The comparison between the proposed DML approach and the previous approach adopting complex IQ modulator (IQM) shows similar filter flexibility, shape fidelity and noise performance, proving that the DML-based Brillouin filter technique is a cost-effective and valid solution for microwave photonic applications.

Solitons in a $\PT$- symmetric $\chi^{(2)}$ coupler

Magnus Ogren, Fatkhulla Abdullaev, and Vladimir Konotop

Doc ID: 305223 Received 22 Aug 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: We consider the existence and stability of solitons in a $\chitwo$ coupler. Both the fundamental and second harmonics undergo gain in one of the coupler cores and are absorbed in the other one. The gain and losses are balanced creating a parity-time ($\PT$) symmetric configuration. We present two types of families of $\PT$-symmetric solitons, having equal and different profiles of the fundamental and second harmonics. It is shown that gain and losses can stabilize solitons. Interaction of stable solitons is shown. In the cascading limit the model is reduced to the $\PT$-symmetric coupler with effective Kerr-type nonlinearity and balanced nonlinear gain and losses.

Characterization of depolarizing samples based on the indices of polarimetric purity

Albert Van Eeckhout, Angel Lizana, Enric Garcia-Caurel, Jose Gil, Razvigor Ossikovski, and Juan Campos

Doc ID: 301660 Received 05 Jul 2017; Accepted 12 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: In this work we discuss the interest of using the Indices of Polarimetric Purity (IPPs) as a criterion for the characterization and classification of depolarizing samples. We proved how differences in the depolarizing capability of samples, not seen by the commonly used depolarization index PΔ, are identified by the IPPs. The above-stated result is analyzed from a theoretical point of view, and experimentally verified through a set of polarimetric measurements. We show how the approach here presented can be useful to easily synthetize depolarizing materials with controlled depolarizing features, just by properly combining low-cost fully polarizing materials (as linear retarders or polarizers).

Efficient wavelength conversion with low operation power in Ta₂O₅ based micro-ring resonator

Chung-Lun Wu, Jen-Yang Huang, Ding-Hsin Ou, Ting-Wei Liao, Yi-jen Chiu, Min-Hsiung Shih, YuanYao Lin, Ann-Kuo Chu, and Chao-Kuei Lee

Doc ID: 302655 Received 17 Jul 2017; Accepted 12 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: The Ta₂O₅ based micro-ring resonator with unloaded quality factor of ~182000 has been demonstrated to realize efficient nonlinear wavelength generation. The propagation loss of Ta₂O₅ based micro-ring resonator is 0.5/cm, and the buildup factor of ring resonator is estimated to be ~50. With a high buildup factor of ring structure, the four-wave-mixing (FWM) conversion efficiency of -30dB is achieved in the Ta₂O₅ based micro-ring resonator with pump power of 6mW. Based on a power-dependent FWM results, the nonlinear refractive index of Ta₂O₅ is estimated to be 1.4E-14 cm²/W at wavelength of ~1550nm. The demonstration of enhanced FWM process in the Ta₂O₅ based micro-ring cavity implies the possibility of realizing FWM based optical parametric oscillation in Ta₂O₅ based micro-ring resonator.

Fast and accurate modelling of nonlinear pulse propagation in graded-index multimode fibers

Matteo Conforti, Carlos Mas Arabi, Arnaud Mussot, and Alexandre Kudlinski

Doc ID: 304209 Received 04 Aug 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: We develop a model for the description of nonlinear pulse propagation in multimode optical fibers with a parabolic refractive index profile. It consists in a 1+1D generalized nonlinear Schrodinger equation with a periodic nonlinear coefficient, which can be solved in an extremely fast and efficient way. The model is able to quantitatively reproduce recently observed phenomena like geometric parametric instability and broadband dispersive wave emission. We envisage that our equation will represent a valuable tool for the study of spatiotemporal nonlinear dynamics in the growing field of multimode fiber optics.

Intensity noise suppression in mode-locked fiber lasers by double optical bandpass filtering

Dohyun Kim, Shuangyou Zhang, Dohyeon Kwon, Ruoyu Liao, Yifan Cui, Zhigang Zhang, Youjian Song, and Jungwon Kim

Doc ID: 304758 Received 14 Aug 2017; Accepted 12 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: We show that the relative intensity noise (RIN) of a mode-locked fiber laser can be suppressed below -140 dB/Hz level for the entire >20-Hz offset frequency range by a proper combination of intra-cavity and extra-cavity optical bandpass filters. When a 12-nm-bandwidth intra-cavity filter and a 16-nm-bandwidth extra-cavity filter are employed for a polarization-maintaining-nonlinear-amplifying-loop-mirror (PM-NALM)-based Er-fiber laser, the RIN spectrum level is suppressed by ~30 dB in the low offset frequency range. The resulting integrated rms RIN is only 0.0054% [1 Hz – 1 MHz], which is, to our knowledge, one of the lowest integrated RIN performances for any mode-locked lasers reported so far. Besides the simplicity, this double filtering approach has an additional advantage that, unlike active pump-laser feedback methods, it does not have any resonant peaks in the stabilized RIN spectrum. In addition to the RIN suppression, with intra-cavity bandpass filtering, the integrated rms timing jitter is also reduced from 7.29-fs (no-filter) to 2.95-fs (12-nm intra-cavity filter) [10 kHz – 1 MHz] in the soliton PM-NALM laser.

A photoacoustic imaging methodology for the optical characterization of contact lenses

George Tserevelakis, Margarita Tsagkaraki, Miltiadis Tsilimbaris, Sotiris Plainis, and Giannis Zacharakis

Doc ID: 303700 Received 14 Aug 2017; Accepted 12 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: We demonstrate photoacoustic microscopy as a metrology method for the optical characterization and quality control of Contact Lenses (CL). Dual wavelength excitation is applied to CLs tinted on either side with two thin ink layers, each of them possessing distinctly different optical absorption properties. The method is thus capable of measuring the elevation maps of both CL surfaces during two subsequent imaging sessions and extract the CL thickness, curvatures and dioptric power. We show that such an easily implementable technique provides robust, high precision, cost effective 3D imaging and characterization of both rigid and soft CLs, which render it highly favorable for a broad range of applications.

Generation, amplification, frequency conversion and reversal of propagation of THz photons in nonlinear hyperbolic metamaterial

Alexander Popov and Sergey Myslivets

Doc ID: 301495 Received 04 Jul 2017; Accepted 11 Sep 2017; Posted 15 Sep 2017  View: PDF

Abstract: The metamaterial is proposed which supports a mixture of three or more normal and backward electromagnetic modes with equal co-directed phase velocities and mutually contra-directed energy fluxes. This enables extraordinary three-wave mixing, greatly enhanced optical parametric amplification and frequency-changing generation of entangled photons in the reflection direction. Proof-of-principle numerical simulation of such processes is presented based on the particular example of the wave-guided THz waves contra-propagating in the metamaterial made of carbon nanotubes.

Study of femtosecond laser induced circular optical properties in silica by Mueller matrix spectropolarimetry

Jing TIAN, Matthieu Lancry, SangHyuk YOO, Enric Garcia-Caurel, Razvigor Ossikovski, and Bertrand Poumellec

Doc ID: 305152 Received 18 Aug 2017; Accepted 11 Sep 2017; Posted 15 Sep 2017  View: PDF

Abstract: Transmission Mueller-matrix spectroscopic ellipsometry is applied to femtosecond laser induced modifications in silica glass in the spectral range 450–1000 nm. Within type II regime, the modifications exhibit not only circular dichroism but also circular birefringence. We suggest that the laser polarization orientation with respect to pulse front tilt determines the amplitude and the sign of the circular properties. By using differential decomposition of the Mueller matrix, optical rotation is revealed for the first time. A maximum value of the effective optical activity of 143°/mm at 550 nm is found.

Polarization-independent metalens constructed of antennas without rotational invariance

Hui Yang, Guanhai Li, Guangtao Cao, Zengyue Zhao, Feilong Yu, Xiaoshuang Chen, and Wei Lu

Doc ID: 305821 Received 28 Aug 2017; Accepted 11 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We proposed a novel approach to design an ultra-thin polarization-independent metalens (PIM) by utilizing antennas without rotational invariance. Two arrays of nanoblocks are elaborately designed to form the super cell of the PIM, which are capable of focusing right-handed circularly polarized (RCP) and left-handed circularly polarized (LCP) lights, respectively. With such a strategy, the PIM is able to achieve polarization-independent focusing since the light with any polarization can be treated as a combination of the two orthogonal ones. A theoretical analysis based on the Jones vector is proposed to detailedly explore the underlying physics. The polarization-independent characteristic of the designed PIM is also demonstrated by utilizing the finite difference time domain (FDTD) simulations. Moreover, polarization-independent focusing can be achieved within a wavelength range of 400nm. These results can deepen our understanding of polarization-independent focusing and provide a new method to design ultra-thin polarization-independent devices.

Endoscopic optical coherence tomography with focus adjustable probe

Wenchao Liao, Tianyuan Chen, Chengming Wang, Wenxin Zhang, Zhangkai Peng, Xiao Zhang, Shengnan Ai, Deyong Fu, TieYing ZHOU, and Ping Xue

Doc ID: 303780 Received 01 Aug 2017; Accepted 11 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: We present a focus adjustable endoscopic probe for optical coherence tomography (OCT), which is able to acquire images with different focal planes and overcome depth of focus limitations by image fusing. The use of two-way shape-memory-alloy spring enables the probe to adjust working distance over 1.5mm, providing large scanning range with high resolution and no sensitivity loss. Equipped with home-made hollow-core ultrasonic motor, the probe is capable of performing an unobstructed 360 degrees field-of-view distal scanning. The axial resolution and best lateral resolution are both ~4μm, with a sensitivity of 100.3dB. Spectral-domain OCT imaging of phantom and biological tissues with the probe is also demonstrated. © 2017 Optical Society of AmericaOCIS codes: (170.4500) Optical coherence tomography; (170.2150) Endoscopic imaging; (170.3880) Medical and biological imaging; (220.0220) Optical design and fabrication; (220.4000) Microstructure fabrication; ( 0.3990) Micro-optical devices.

Generation of Two-Mode Frequency Degenerate Twin Beams in ⁸⁵Rb Vapor

jun jia, Wei Du, Jiefei Chen, Chunhua Yuan, Zhe-Yu Ou, and Weiping Zhang

Doc ID: 302872 Received 24 Jul 2017; Accepted 11 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We demonstrate a new phase-matching scheme for four-wave mixing processes in hot ⁸⁵Rb vapor, in which all four fields propagate in different directions but two of them are degenerate in frequency. When used as a parametric amplifier with an injected seed, two types of quantum mechanically correlated twin-beam states, either frequency degenerate or nondegenerate, can be generated. The quantum noise reduction in the intensity difference is almost 7 dB for the nondegenerate type and nearly 5 dB for the degenerate type over a wide frequency range. The spatial nondegeneracy of the four waves allows a variety of configurations of parametric processes, leading to flexible control for both phase insensitive and sensitive parametric amplification. The spatially nondegenerate but frequency degenerate four-wave mixing process will find wide applications in quantum metrology, quantum communication and quantum information of continuous variables.

A low cost 3D printed 1 nm resolution smartphone sensor based spectrometer: instrument design and application in ultraviolet spectroscopy

Thomas Wilkes, Andrew McGonigle, Jon Willmott, Tom Pering, and Joseph Cook

Doc ID: 304126 Received 04 Aug 2017; Accepted 11 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We report on the development of a low cost spectrometer, based on off-the-shelf optical components, a 3D printed housing and a modified Raspberry Pi camera module. With a bandwidth and spectral resolution of ≈ 60 nm and 1 nm, respectively, this device was designed with ultraviolet (UV) remote sensing of atmospheric sulphur dioxide (SO2), ≈ 310 nm, in mind. To the best of our knowledge, this is both the first report of a UV spectrometer, and of a nanometer resolution spectrometer, based on smartphone sensor technology. The spectrometer’s performance was assessed and validated by measuring the column amounts of SO2 within quartz cells, with a differential optical absorption spectroscopy processing routine. This system could easily be reconfigured to cover other spectral regions in the UV-visible-near-IR, as well as to provide alternate spectral ranges and/or linewidths. Hence, whilst a particular UV application area is documented here, our intention is also to highlight how this framework could be applied to build bespoke, low-cost, spectrometers for a range of other scientific applications.

Plasmonic Topological Insulators For Topological Nanophotonics

Weifeng Zhang, Xianfeng Chen, and Fangwei Ye

Doc ID: 301194 Received 28 Jun 2017; Accepted 10 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: Photonic topological insulators are optical structures supporting robust propagation of light at their edges that are topologically protected from scattering. Here we propose the concept of plasmonic topological insulators that not only topologically protect light at the lattice edges but also enable their confinement and guidance at the deep-subwavelength scale. The suggested plasmonic topological insulators are composed of evanescently coupled array of metallic nanowires that are modulated periodically along the light propagation direction. The intrinsic loss associated with the plasmonic topological insulators is found not to deteriorate their topological protection on the edge modes. The marriage of topological photonics with nanophotonics opens up the possibility of topological nanophotonics.

Continuous tunable broadband emission of fluorphosphate glasses for single-component multi-chromatic phosphors

Ruilin Zheng, Qi Zhang, Ke-Han Yu, Chunxiao Liu, Jianyong Ding, Peng Lv, and Wei Wei

Doc ID: 304835 Received 18 Aug 2017; Accepted 09 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: A kind of Sn2+/Mn2+ co-doped fluorphosphate (FP) glasses served as single-component continuous tunable broadband emitting multi-chromatic phosphors are developed for the first time. Importantly, these FP glasses have high thermal conductivity (3.25-3.70 W/m·K) and good chemical stability in water (80 oC). By combining with commercially available UV-LEDs directly, the emission colors can be tuned from blue/cold-white to warm-white/red through the energy transfer from Sn2+ to Mn2+, and the broadband spectra covering whole visible region from 380 nm to 760 nm. Notably, the FP glass can also service as a white light phosphor by controlling the content of SnO/MnO, which has excellent optical properties that, CIE chromaticity coordinate, CRI and QE are (0.33, 0.29), 84 and 0.952, respectively. These new phosphors, possessing of good optical and chemical properties, are promising for applications in solid-state lighting devices.

Fabrication of disk droplets and evaluation of their lasing action

Mitsunori Saito, Takuya Hashimoto, and Jumpei Taniguchi

Doc ID: 302764 Received 18 Jul 2017; Accepted 09 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: Disk resonators are difficult to create with droplets, since they self-form spheres due to the surface tension. In this study, disk (cylindrical) droplets were created by enclosing a dye (rhodamine 6G) solution in silicone rubber. Lasing actions of these droplets were examined by pulsed green laser excitation. In a large droplet (2 mm diameter), the whispering gallery mode emission was difficult to attain, since it competed with the radial or axial modes that made a round trip in the droplet. A disk droplet of 150 μm diameter exhibited a comb-like spectrum of the whispering gallery mode resonant emission.

Adaptive Pre-Amplification Pulse Shaping in aHigh-Power, Coherently Combined Fiber Laser System

Nils Becker, Steffen Hadrich, Tino Eidam, Florian Just, Karoly Osvay, Zoltan Várallyay, Jens Limpert, Andreas Tünnermann, Thomas Pertsch, and Falk Eilenberger

Doc ID: 301803 Received 27 Jul 2017; Accepted 08 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: We report on the successful implementation of a highly efficient adaptive pulse shaping technique in the ELI-HR high-power laser source. The pulse shaper is utilized to impose a gain flattening mask to increase the spectral width of the amplified pulse. Simultaneously, it pre-compensates for high order dispersion, acquired during stretching, multi-stage amplification and subsequent compression of the 8-channel, coherently combined main amplification stage. This result is expected to significantly enhance the performance of the fiber laser system and the subsequent nonlinear compression stages.

New classes of non-parity-time-symmetric optical potentials with all-real spectra and exceptional-point-free phase transition

Jianke Yang

Doc ID: 302381 Received 13 Jul 2017; Accepted 07 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: Paraxial linear propagation of light in an optical waveguide with material gain and loss is governed by a Schr\"odinger equation with a complex potential. Properties of parity-time-symmetric complex potentials have been heavily studied before. In this article, new classes of non-parity-time-symmetric complex potentials featuring conjugate-pair eigenvalue symmetry in its spectrum are constructed by operator symmetry methods. Due to this eigenvalue symmetry, it is shown that the spectrum of these complex potentials is often all-real. Under parameter tuning in these potentials, phase transition can also occur, where pairs of complex eigenvalues appear in the spectrum. A peculiar feature of the phase transition here is that, the complex eigenvalues may bifurcate out from an interior continuous eigenvalue inside the continuous spectrum, in which case a phase transition takes place without going through an exceptional point. In one spatial dimension, this class of non-parity-time-symmetric complex potentials is of the form $V(x)=h'(x)-h^2(x)$, where $h(x)$ is an arbitrary parity-time-symmetric complex function. These potentials in two spatial dimensions are also derived. Diffraction patterns in these complex potentials are further examined, and unidirectional propagation behaviors are demonstrated.

Highly Sensitive Demodulation of Vibration-induced Phase Shift Based on a Low Noise OEO

Xiaofeng Jin, Zhu Yanhong, Jiaojiao Guo, Xiangdong Jin, Xianbin Yu, Shilie Zheng, Hao Chi, and Xianmin Zhang

Doc ID: 301341 Received 30 Jun 2017; Accepted 07 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: A highly sensitive demodulation approach of vibration induced phase shift based on a low noise optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The vibration induced optical phase variation is directly converted to the electrical oscillating signal of OEO with carrier phase-shifted double sideband (CPS-DSB) modulation, which is realized by cascading a dual-output Mach-Zehnder modulator (DOMZM) and a fiber interferometer. Theoretically, within CPS-DSB modulated OEO, the minimum detectable optical phase shift is determined by the phase noise achievable and the sensitivity of optical phase shift demodulation no longer depends on its frequency. A proof-of-concept OEO oscillating at 100 MHz with ultralow phase noise is built up for demonstration. The achieved minimum detectable optical phase shift is 0.58 μrad at 1 kHz and 0.21 μrad at 10 kHz, which are the best results ever reported.

Phase-measuring time-gated BOCDA

Alexia Lopez-Gil, Sonia Martin-Lopez, and Miguel Gonzalez Herraez

Doc ID: 301172 Received 30 Jun 2017; Accepted 07 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: We demonstrate a simple scheme allowing to perform distributed Brillouin Phase Shift (BPS) measurements with very high spatial resolution (~ 7 cm) over long (~ 4.7 km) optical fibers. This is achieved by inserting a Sagnac interferometer (SI) in a Brillouin Optical Correlation Domain Analysis (BOCDA) configuration. Over its already-presented time-domain equivalent (SI-BOTDA), this approach reduces the main source of noise (coherent backscatter noise) thanks to the low-coherence nature of the used signals. On the other hand, over the most usual schemes used for distributed BPS measurements, this implementation presents the key advantage of not requiring high-bandwidth detection or complex modulation, while reaching unprecedented values of spatial resolution and number of resolved points for this type of measurements. Thanks to the linear dependence of the BPS feature around the Brillouin Frequency Shift (BFS), this scheme could also have the advantage of requiring shorter scanning ranges than amplitude-based configurations.

Mid-infrared 1 Watt hollow-core fiber gas laser source

Mengrong Xu, Fei Yu, and Jonathan Knight

Doc ID: 301281 Received 03 Jul 2017; Accepted 07 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: We report the characteristics of a 1 Watt hollow-core fiber gas laser, emitting continuous-wave in the mid-infrared. Our system is based on an acetylene-filled hollow-core optical fiber, guiding with low losses at both the pump and laser wavelengths and operating in the single-pass ASE regime. By systematic characterization of the pump absorption and output power dependence on gas pressure, fiber length and pump intensity, we determine that the reduction of pump absorption at high pump flux and the degradation of gain performance at high gas pressure necessitate the use of increased gain fiber length for efficient lasing at higher powers. Low fiber attenuation is therefore key to efficient high-power laser operation. We demonstrate 1.1 Watt output power at 3.1 m wavelength from a single-pass configuration using a fiber length of 15 m at a pressure of 0.6 mbar, approximately 400 times higher CW output power than in the ring cavity previously reported.

Achieving comb formation over the entire lasing range of quantum cascade lasers

Yang Yang, David Burghoff, John Reno, and Qing Hu

Doc ID: 297094 Received 31 May 2017; Accepted 06 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: Frequency combs based on quantum cascade laser (QCL) are finding promising applications in high-speed broadband spectroscopy in the terahertz regime, where many molecules have their “fingerprints”. To form stable combs in QCLs, an effective control of group velocity dispersion plays a critical role. The dispersion of the QCL cavity has two main parts: a static part from the material and a dynamic part from the intersubband transitions. Unlike the gain, which is clamped to a fixed value above the lasing threshold, dispersion associated with the intersubband transitions changes with bias even above the threshold, and this reduces the dynamic range of comb formation. Here, by incorporating tunability into the dispersion compensator, we demonstrate a QCL device exhibiting comb operation from Ith to Imax, which greatly expands the operation range of the frequency combs.

High-precision active synchronization control of high-power, tiled-aperture coherent beam combining

Peng Chun, Xiaoyan Liang, Ruxin Li, Li Wenqi, and Renqi Liu

Doc ID: 301799 Received 13 Jul 2017; Accepted 06 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We propose and demonstrate a high-precision active control technique for tiled-aperture coherent beam combining suitable for high-power laser pulses. The method is a hybrid structure based on the near-field interference fringe technique and single-crystal balanced optical cross-correlation, which enables the active loop to exhibit high accuracy, wide dynamic range, and good capacity for resisting energy disturbance. In the proof-of-principle experiment, we realized an adjustable beam combing bandwidth of approximately 100 Hz (limited by the speed of the piezo-electric transducer) and root-mean-square deviation of approximately λ/51 for two beam channels with a combining efficiency of 93%.

Two-photon saturable absorption properties and laser Q-switch application of carbon quantum dots

shande Liu, Qiangguo Wang, Kai Wang, Yongping Yao, huiyun zhang, Tingqi Ren, Zhengmao Yin, Fanglin Du, Baitao Zhang, and Jingliang He

Doc ID: 304905 Received 21 Aug 2017; Accepted 06 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: In this paper, high-quality carbon quantum dots (CQDs) with an average size of 15 nm are synthesized by using a solvothermal method. A CQDs saturable absorber mirror (SAM) was prepared, characterized and employed as an ultrafast optical switch successfully in a 1.0 μm solid-state laser. The saturable absorption effect (at 1 μm) far away from linear absorption band of the CQDs could be attributed to two-photon saturable absorption. The modulation depth (ΔT) and saturable energy intensity (Φs) of the CQDs-SA was measured about 4% and 15.34W/mm2, respectively. By using this SA, a Q-switched Nd:GdVO4 laser at 1 μm is firstly realized with the shortest pulse width of 66.8 ns and the maximum repetition rate of 1.13 MHz, respectively. The results indicate that CQDs may found to be another decent carbon SA materials for the applications in visible and infrared band.

Modeling and calibrating nonlinearity and crosstalk in back focal plane interferometry for three-dimensional position detection

Peng Cheng, Sissy Jhiang, and Chia-Hsiang Menq

Doc ID: 303198 Received 27 Jul 2017; Accepted 06 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: Back focal plane (BPF) interferometry is frequently used to detect the motion of a single laser trapped bead in photonic force microscope (PFM) system. Whereas this method enables high-speed and high-resolution position measurement, its measurement range is limited by nonlinearity coupled with crosstalk in three-dimensional (3-D) measurement and validation of its measurement accuracy is not trivial. This article presents an automated calibration system in conjunction with a 3-D quadratic measurement sensitivity model to render rapid and accurate calibration of the laser measurement system. An actively controlled 3-axis laser steering system and a high-speed vision-based 3-D particle tracking system are integrated to the PFM system to enable automatic and rapid calibration. The 3-D nonlinear model is utilized to correct for nonlinearity and crosstalk, and thus extend the 3-D position detection volume of back focal plane interferometry. We experimentally demonstrated a 12-fold increase in detection volume when applying the method to track the motion of a 2.0 µm laser trapped polystyrene bead.

Tunable Coffee-Ring Effect on Superhydrophobic Surface

An He, Huan Yang, Wei Xue, Ke Sun, and Yu Cao

Doc ID: 303260 Received 28 Jul 2017; Accepted 06 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: A tunable coffee-ring effect (CRE) that enables patterned deposition of nanoparticles (NPs) is obtained on the designed superhydrophilic and superhydrophobic composite surface of the titanium substrate. The low-adhesion superhydrophobic (LASH) surfaces with picosecond (ps) laser induced periodic surface structure (LIPSS) and micro-nano hierarchical structure (MNHS) are investigated. The NPs are not only deposited in a bitty area of 0.045mm² which is 265.56 times smaller than that of the original hydrophilic surface, but also in various patterns such as triangle, rectangle, eclipse besides the traditional circular shape. This controllable morphology of the CRE indicates a maneuvering capability of NPs in their common preservation form of suspension turbid liquid even when the solution concentration reaches 1 mg/mL, which is promising for the NPs printed circuit boards and the site-specific delivery drugs.

Wedge-shaped semiconductor nanowall arrays with excellent light management

Xinyu Chen, Jiang Wang, Shengchun Qin, Qiang Chen, Yali Li, Junshuai Li, and Deyan He

Doc ID: 304369 Received 09 Aug 2017; Accepted 06 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: In this Letter, a light management structure composed of wedge-shaped semiconductor nanowall arrays is introduced. Theoretical investigation based on gallium arsenide (GaAs) indicates that a 1000 nm high array (wall base width/array periodicity: 500 nm) with an effective thickness of only 500 nm can deliver a maximum photocurrent density (Jph) of ~ 29.0 mA/cm2 at AM1.5G illumination (for an ideal absorber with the same bandgap, the corresponding value is ~ 32.0 mA/cm2.). However, Jph of a 1500 nm thick flat GaAs film is only ~ 19.2 mA/cm2 at the same illumination condition. The wedge-shaped nanowall arrays meanwhile exhibit good omnidirectional light confinement. At the incident angle of 60°, Jph of the aforementioned nanowall array is ~ 12.7 mA/cm2, and the corresponding value for an ideal absorber is ~ 16.0 mA/cm2. Considering the simple structure and excellent light confinement in a broad range of the system parameters including array periodicity, nanowall height and incident angle of light, the wedge-shaped semiconductor nanowall arrays provide a valuable platform for fabricating the related high performance-to-cost semiconductor optoelectronic devices.

Ultra-broadband mode filters based on graphene-embedded waveguides

Zeshan Chang and Kin Chiang

Doc ID: 303195 Received 24 Jul 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: We propose spatial-mode filters based on embedding graphene films in optical waveguides. To demonstrate the effectiveness and the flexibility of this approach, we design and fabricate several mode filters where graphene films of different widths and lengths are placed in different locations of polymer waveguides. Our mode filters are easy to make and can provide high mode extinction ratios that are insensitive to the operation wavelength. Such mode filters could find applications in broadband mode-division-multiplexing transmission systems and other areas that involve mode selection or stripping.

Capillary Red Blood Cell velocimetry by Phase-resolved Optical Coherence Tomography

Jianbo Tang, Sefik Evren Erdener, Buyin Fu, and David Boas

Doc ID: 305742 Received 28 Aug 2017; Accepted 05 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: We present a phase-resolved Optical Coherence Tomography (OCT) method to extend Doppler OCT for accurate measurement of the red blood cell (RBC) velocity in cerebral capillaries. OCT data was acquired with an M-mode scanning strategy (repeated A-scans) to account for the single file passage of RBCs in a capillary, and then high pass filtered to remove the stationary component of the signal to ensure accurate measurement of phase shift of flowing RBCs. The angular frequency of the signal from flowing RBCs was then quantified from the dynamic component of the signal, and used to calculate the axial speed of flowing RBCs in capillaries. We validated our measurement by RBC passage velocimetry using the signal magnitude of the same OCT time series data.

Measuring the electromagnetic chirality of 2D arrays under normal illumination

Xavier Garcia Santiago, Sven Burger, Carsten Rockstuhl, and Ivan Fernandez-Corbaton

Doc ID: 305177 Received 18 Aug 2017; Accepted 05 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: We present an electromagnetic chirality measure for 2D arrays of subwavelength periodicities under normal illumination. The calculation of the measure uses only the complex reflection and transmission coefficients from the array. The measure allows the ordering of arrays according to their electromagnetic chirality, allowing a quantitative comparison of different design strategies. The measure is upper bounded, and the extreme properties of objects with high values of electromagnetic chirality make them useful in both near- and far-field applications. We analyze the consequences that different possible symmetries of the array have on its electromagnetic chirality. We use the measure to study four different arrays. The results indicate the suitability of helices for building arrays of high electromagnetic chirality, and the low effectiveness of a substrate for breaking the transverse mirror symmetry.

Ramsey interferometry of a bosonic Josephson junction in an optical cavity

Sheng-Chang Li, Fu-Quan Dou, and Li-Bin Fu

Doc ID: 301357 Received 04 Jul 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: We investigate the nonlinear Ramsey interferometry of a bosonic Josephson junction coupled to an optical cavity by applying two identical pumping field pulses separated by a holding field in the time domain. When theholding field is absent, we show that the atomic Ramsey fringes are sensitive to both the cavity-pump detuning and the initial state, and their periods can encode the information on both the atom-field coupling andthe atom-atom interaction. For a weak holding field, we find that the fringes characterized by the oscillation of the intra-cavity photon number can completely reflect the frequency information of the atomic interferencedue to the weak atom-cavity coupling. This finding allows a nondestructive observation of the atomic Ramsey fringes via the cavity transmission spectra.

Single camera shot interferenceless coded aperture correlation holography

Mani Rai, Vijayakumar Anand, and Joseph Rosen

Doc ID: 302253 Received 12 Jul 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: We propose a new scheme for recording an incoherent digital hologram by a single camera shot. The method is based on a motionless, interferenceless, coded aperture correlation holography for 3D imaging. Two random-like coded phase masks (CPMs) are synthesized using Gerchberg-Saxton algorithm with two different initial random phase profiles. The two CPMs are displayed side by side and used as the system aperture. Light from a pinhole is introduced into the system and two impulse responses are recorded corresponding to the two CPMs. The two impulse responses are subtracted and the resulting intensity profile is used as a reconstructing hologram. A library of reconstructing holograms is created corresponding to all possible axial locations. Following the above training stage, an object is placed within the axial limits of the library and the intensity patterns of a single shot, corresponding to the same two CPMs, are recorded under identical conditions to generate the object hologram. The image of the object at any plane is reconstructed by a cross-correlation between the object hologram and the corresponding reconstructing hologram from the library.

Engineering steady-state entanglement via dissipation and quantum Zeno dynamics in optical cavity

Dong Xiao Li, xq shao, Jin-Hui Wu, and x. x. yi

Doc ID: 302318 Received 14 Jul 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: A new mechanism is proposed for dissipatively preparing maximal Bell entangled state of two atoms in an optical cavity. This scheme integrates the spontaneous emission, the light shift of atoms in the presence of dispersive microwave field, and the quantum Zeno dynamics induced by continuous coupling, to obtain a unique steady state irrespective of initial state. Even for a large cavity decay, a high-fidelity entangled state is achievable at a short convergence time, since the occupation of cavity mode is inhibited by the Zeno requirement. Therefore, a low single-atom cooperativity $C=g^2/(\kappa\gamma)$ is good enough for realizing a high fidelity of entanglement in a wide range of decoherence parameters. As astraightforward extension, the feasibility for preparation of two-atom Knill-Laflamme-Milburn state with the same mechanism is also discussed.

Radial-variant nonlinear ellipse rotation

Bo Wen, Yuxiong Xue, Gu Bing, Guanghao Rui, jun He, and Yiping Cui

Doc ID: 305261 Received 21 Aug 2017; Accepted 04 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: The nonlinear ellipse rotation usually occurs when an elliptically polarized beam propagates through an isotropic nonlinear medium owing to the existence of χ₁₂₂₁ . Here we report the radial-variant nonlinear ellipse rotation of a vector beam with structured elliptical polarization through isotropic Kerr nonlinearities. Due to the interaction of elliptically polarized vector beams (EPVBs) with isotropic nonlinear media, the distributions of both the orientation angle and the ellipticity angle of beams at the far-field observational plane exhibit multiple concentric ring structures with the circularly symmetry. Numerical simulations show that the self-diffraction intensity pattern, the distribution of state of polarization, and the spin angular momentum (SAM) distribution of an EPVB could be manipulated by tuning both the isotropic optical nonlinearity and the chirality parameter of the vector beam, which may find direct applications in polarization-control optical switching, SAM manipulation, and optical polarization encoding or detection.

An extended polar decomposition method of Mueller matrices for birefringent turbid media

Ji Qi, Honghui He, Hui Ma, and Daniel Elson

Doc ID: 297981 Received 15 Jun 2017; Accepted 03 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: The polar decomposition method for Mueller matrices proposed by Lu-Chipman has been demonstrated and validated for many applications. However, in some situations, the method may suffer from limitations due to the assumptions required by this method. Here we extended Lu-Chipman’s method and show that it can also be used to analyze turbid media where the scatterer sizes are comparable to or larger than the wavelength in reflection geometry. The method has been validated with experiments on turbid media. This work may thus prove useful in tissue polarimetry.

Broad bandwidth and large fabrication tolerance polarization beam splitter based on anti-symmetric Bragg sidewall gratings in a multimode waveguide

Huiye Qiu, Jiang jianfei, Ping Yu, Jianyi Yang, hui Yu, and Xiaoqing Jiang

Doc ID: 302524 Received 17 Jul 2017; Accepted 03 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: A novel polarization beam splitter (PBS) based on an anti-symmetric sidewall Bragg grating in a multimode silicon-on-insulator strip waveguide is demonstrated. Anti-symmetric spatially periodic refractive-index perturbations are designed for strong coupling between the fundamental (TE0) and the first-order transverse electric modes (TE1), while not for TM modes. An adiabatic coupler is cascaded at the input-port so as to drop the TE1 reflection. The Bragg grating has a compact length of ~20 μm (55 periods). The polarization isolations of the through- and drop-ports at the wavelength of 1557 nm are 34 dB and 31 dB, respectively. A broad bandwidth of 64 nm and a large fabrication tolerance of 80 nm for polarization isolation over 20 dB are also achieved.

Mueller matrix polarimetry on a Young's double slit experiment analogue

Oriol Arteaga, Razvigor Ossikovski, Ertan Kuntman, mehmet kuntman, Adolfo Canillas, and Enric Garcia-Caurel

Doc ID: 297976 Received 12 Jun 2017; Accepted 03 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: In this Letter we describe an experiment in which coherent light is sent through a calcite crystal that separates the photons by their polarization. The two beams are then let to superpose and this recombined beam is used to measure the Mueller matrix of the system. Results are interpreted according to our recent formalism of coherent superposition in material media. This is the first experimental implementation of a Young's experiment with complete polarimetry and it is demonstrated that our method can be used for the experimental synthesis of optical devices with on-demand optical properties.

Photonically Assisted Microwave Waveforms Generation by Gain-Transparent SBS Induced Carrier Processing

Jie Liu, Chaoran Huang, and Chester C.T. Shu

Doc ID: 303264 Received 26 Jul 2017; Accepted 03 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: We propose and experimentally demonstrate a new approach to generate microwave waveforms by phase modulation and optical carrier phase processing based on gain-transparent SBS. By properly adjusting SBS induced-phase shift on the carrier and the following group velocity dispersion, microwave waveforms with controllable repetition rates and temporal profiles can be generated. In the experiment, we have successfully generated triangular waveforms at repetition rates of 5.64 and 7.87 GHz, and rectangular waveforms at repetition rates of 5.04 and 7.01 GHz.

Shaping of optical vector beams in three dimensions

CHENLIANG CHANG, Yuan Gao, Jianpei Xia, Shouping Nie, and Jianping Ding

Doc ID: 304382 Received 08 Aug 2017; Accepted 02 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: We present a method of shaping three dimensional (3D) vector beams with prescribed intensity distribution and controllable polarization state variation along arbitrary curves in three dimensions. By employing a non-iterative 3D beam shaping method developed for the scalar field, we use two curved laser beams with mutually orthogonal polarization serving as base vector components with high intensity gradient and controllable phase variation, so that they are collinearly superposed to produce a 3D vector beam. We experimentally demonstrate the generation of 3D vector beams that have polarization gradient (spatially continuous variant polarization state) along 3D curves, which may find applications in polarization-mediated processes such as to drive the motion of micro-particles.

Single-Frequency Low Threshold Linearly Polarized DFB Raman Fiber Lasers

Sébastien Loranger, Vladimir Karpov, Gregory Schinn, and Raman Kashyap

Doc ID: 304725 Received 15 Aug 2017; Accepted 02 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: Distributed feedback (DFB) fiber lasers have been demonstrated to be excellent narrow-linewidth (kHz range) single-frequency laser sources. However, this type of laser is normally limited to rare-earth doped fibers. Raman gain offers an alternative, operating at any arbitrary wavelength. We demonstrate here linearly polarized, single frequency, DFB fiber Bragg grating Raman lasers with the lowest pump threshold of 350 mW, an output power of up to 50 mW at 1120 nm, an 8.5 % slope efficiency, and 300 mW output power at 1178 nm. In the high-power regime, stimulated Brillouin scattering (SBS) plays an important role in the laser dynamics. We also report the characterization of the power profile inside the fiber along its axis through a novel side-scatter technique.

Patterned multilayer metamaterial for fast and efficient photon collection from dipolar emitters

Oksana Makarova, Mikhail Shalaginov, Simeon Bogdanov, Alexander Kildishev, Alexandra Boltasseva, and Vladimir Shalaev

Doc ID: 303875 Received 08 Aug 2017; Accepted 02 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: Solid state quantum emitters are prime candidates for the realization of fast on-demand single-photon sources. The improvement in photon emission rate and collection efficiency for point-like emitters can be achieved by using a near-field coupling to nanophotonic structures. Plasmonic metamaterials with hyperbolic dispersion have previously been demonstrated to significantly increase the fluorescence decay rates from dipolar emitters due to a large broadband density of plasmonic modes supported by such metamaterials. However, the emission coupled to the plasmonic modes must then be outcoupled into the far-field before it succumbs to ohmic losses. We propose a nano-grooved hyperbolic metamaterial that improves the collection efficiency by several times compared to a conventional planar lamellar hyperbolic metamaterial. Our approach can be utilized to achieve broadband enhancement of emission for diverse types of quantum emitters.

Frequency noise reduction performance of a feed-forward heterodyne technique: application to an actively mode-locked laser diode

Mohamed Omar Sahni, Stephane Trebaol, Laurent Bramerie, Michel Joindot, Sean O Duill, Stuart Murdoch, Liam Barry, and Pascal Besnard

Doc ID: 304128 Received 04 Aug 2017; Accepted 02 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We report on the frequency noise reduction performance of a feed-forward technique. The study is based on frequency noise measurements that allow the spectral response of the feed-forward phase noise correction to be determined. The main limitation to the noise compensation is attributed to the local oscillator flicker noise and the noise added by the optoelectronic loop elements. The technique is applied to an actively modelocked laser diode demonstrating, at the output of the system, an optical frequency comb source with 14 comb-lines reduced to sub-kHz intrinsic linewidth.

Resolution enhanced SOFI via structured illumination

Guangyuan Zhao, Cheng Zheng, Cuifang Kuang, and Xu Liu

Doc ID: 305287 Received 23 Aug 2017; Accepted 02 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: By analyzing the statistics of the temporal fluctuations from the blinking emitters, statistics optical fluctuation imaging (SOFI) achieves super-resolution while imposing less constraints on the blinking behavior of the probes and are more suitable for low SNR acquisition than localization methods. However, determined by the square root of cumulation orders, the resolution improvement of SOFI highly restricts its promotion into high resolution observations. In this letter, abandoning the default flat illumination in stochastic imaging methods, we introduce structured illumination (e.g., Gaussian or sinusoidal pattern) into SOFI (SI-SOFI) to render greatly enhanced resolution. Through simulation with parameters of both real acquisition procedure and microscope properties, we examine the feasibility of SI-SOFI and obtain a resolution improvement of 4-6 folds at just 2nd order cumulation. Also, a practical pathway for the SI-SOFI reconstruction is offered.

Simplified Demultiplexing Scheme for Two PDM-IM/DD System Utilizing a Single Stokes Analyzer Over 25-km SMF

yan pan, Lianshan Yan, Anlin Yi, Lin Jiang, Wei Pan, Bing Luo, and Xihua Zou

Doc ID: 303732 Received 31 Jul 2017; Accepted 01 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We propose a four linear states of polarization (SOPs) multiplexed intensity modulation and direct detection (IM/DD) scheme based on two orthogonal polarization division multiplexing On-off keying (PDM-OOK) systems, and a simple demultiplexing algorithm for this scheme is experimentally demonstrated by utilizing only a single Stokes analyzer. At the rate of 4×10-Gbit/s, the experimental results show that the power penalty of proposed scheme is about 1.5-dB compared to the single PDM-IM/DD for back-to-back transmission. Compared to back-to-back, just about 1.7-dB power penalty is required after 25-km Corning® LEAF® optical fiber transmission. Meanwhile, the performance of the polarization tracking is evaluated, and the result show that the BER fluctuation is less than 0.5-dB with a polarization scrambling rate up to 708.75-deg/s.

Type–II superlattice–based extended short–wavelength infrared focal plane array with an AlAsSb/GaSb superlattice etch–stop layer to allow near–visible light detection

Romain Chevallier, Arash Dehzangi, Abbas Haddadi, and Manijeh Razeghi

Doc ID: 303880 Received 01 Aug 2017; Accepted 01 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: A versatile infrared imager capable of imaging the near–visible to the extended short–wavelength infrared (e–SWIR) is demonstrated using e–SWIR InAs/GaSb/AlSb type–II superlattice–based photodiodes. A bi–layer etch–stop scheme consisting of bulk InAs0.91Sb0.09 and AlAs0.1Sb0.9/GaSb superlattice layers is introduced for substrate removal from the hybridized back–side illuminated photodetectors. The implementation of this new technique on an e–SWIR focal plane array results in a significant enhancement in the external quantum efficiency in the 1.8 to 0.8 μm spectral region while maintaining high quantum efficiency at the wavelengths longer than 1.8 μm. Test pixels exhibit 100% cut–off wavelengths of ~2.1 and ~2.25 μm at 150 and 300 K, respectively. They achieve saturated quantum efficiency values of 56% and 68% at 150 and 300 K, respectively, under back–side illumination and without any anti–reflection coating. At 150 K, the photodetectors (27×27 μm2 area) exhibit a dark current density of 4.7×10-7 A/cm2 under −50 mV applied bias providing a specific detectivity of 1.77×1012 cm•Hz1/2/W. At 300 K, the dark current density reaches 6.6×10-2 A/cm2 under -50 mV bias, providing a specific detectivity of 5.17×109 cm•Hz1/2/W.

OAM beam excitation using all-fiber weakly-fused mode selective coupler

Shankar Pidishety, Pachava Srinivas, Patrick Gregg, Siddharth Ramachandran, Gilberto Brambilla, and Balaji Srinivasan

Doc ID: 292548 Received 10 Apr 2017; Accepted 01 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: OAM beam excitation through direct phase-matched coupling is experimentally demonstrated using an all-fiber weakly-fused mode selective coupler consisting of a single mode fiber and a ring-core vortex fiber. Experimental results showing the excited OAM mode purity of up to 75% measured through the standard ring technique not only demonstrates the proof of concept, but also provides a baseline for further improvement.

Surface exciton polaritons supported by a J-aggregate-dye/air interface at room temperature

Kentaro Takatori, Takayuki Okamoto, Koji Ishibashi, and Ruggero Micheletto

Doc ID: 302978 Received 20 Jul 2017; Accepted 01 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: Surface exciton polaritons (SEPs) are very important for the realization of novel sensors and next generation optical devices. Here we propose for the first time a Kretschmann-Raether device able to induces SEPs propagating along the interface between J-aggregate cyanine dye and air, at room temperature. This configuration has the advantage to be straightforward to realize and easy to study, because the Kretschmann-Raether approach is the most simple and fundamental from the theoretical point of view. Here, J-aggregate cyanine dye produces strong binding energy due to Frenkel excitons, and this enables observation of SEPs easily at room temperature. One of the advantages of the use of J-aggregate cyanine dye is the simple device preparation. This is because the J-aggregate cyanine dye can be easily deposited on any arbitrary substrates with spincoating or dip-coating technique from its aqueous solution in ambient condition. We observed SEPs at room temperature, and the deepest resonant peak was obtained for a 94-nm thick 5,6-dichloro-2-[[5,6-dichloro-1-ethyl-3-(4-sulfobutyl)-benzimidazol-2-ylidene]-propenyl]-1-ethyl-3-(4-sulfobutyl)-benzimidazolium hydroxide film at 532~nm wavelength. Our results may pave the way for the realization of novel SEPs biosensors in a simple and straightforward way at room temperature.

Axicon-based Bessel beams for flatfield illumination in Total Internal Reflection Fluorescence (AxiTIRF) Microscopy

Benjamin Schreiber, Kareem Elsayad, and Katrin Heinze

Doc ID: 303364 Received 31 Jul 2017; Accepted 01 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: Total internal reflection fluorescence (TIRF) microscopy provides low-invasive high-contrast surface imaging with optical-sectioning of typically 100-200 nm. Thus, TIRF microscopy (TIRF-M) has become an established tool for imaging surfaces including cell membranes. For TIRF-M a homogenous evanescent field of excitation over the whole field of view is generally desired for quantitative microscopy, however not necessarily straight forward to generate when Gaussian beams. In recent years, several improvements on TIRF-M have been developed, which have addressed non-uniform scattering fringes and other artifacts. Here, we introduce a cost-effective TIRF setup with a very low degree of complexity and no moving parts that provides a flat-top like excitation profile. The setup uses a tunable laser ring zoom focus system to generate a full 360° TIRF illumination. Two axicon lenses and one focus lens allow for generation and control of the ring diameter to tune the TIRF excitation angle. We show that 360° laser illumination in combination with a radial polarizer will generate an evanescent Bessel-beam excitation field that exhibits a flat-top intensity over an extended part of the field of view, and demonstrate the advantages of this axicon-based Bessel beams illumination (AxiTIRF) for live-cell imaging.

High-order harmonic generations in intense mid IR fields by cascade 3-wave mixing in a fractal-poled LiNbO3 photonic crystal

Hyunwook Park, Antoine Camper, Kyle Kafka, Boqin ma, Yu Hang Lai, Cosmin Blaga, Pierre Agostini, Louis DiMauro, and Enam Chowdhury

Doc ID: 301219 Received 30 Jun 2017; Accepted 01 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: We report on the generation of harmonic-like photon up-conversion in a LiNbO3-based nonlinear photonic crystal by mid-infrared femtosecond laser pulses. We study below bandgap harmonics of various driver wavelengths, reaching up to 11th order at 4 μm driver with 13% efficiency. We compare our results to numerical simulations based on two mechanisms: cascade 3-wave mixing and non-perturbative harmonic generation, both of which include quasi-phase matching. The cascade model reproduces well the general features of the observed spectrum including a plateau-like harmonic distribution and the observed efficiency. This has the potential for providing a source of tabletop few femtosecond UV pulses.

On-grating graphene surface plasmons enabling spatial differentiation in terahertz region

Zhichao Ruan, Yisheng Fang, and Yijie Lou

Doc ID: 296859 Received 30 May 2017; Accepted 31 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: We propose a graphene-on-grating nanostructure to enable second-order spatial differentiation computation in terahertz (THz) region. The differentiation operation is based on the interference between the direct reflected field and the leakage of two excited surface plasmon polaritons counter-propagating along the graphene sheet. With the spatial coupled-mode theory, we derive out that the requirement for the second-order spatial differentiation is the critical coupling condition. We numerically demonstrate such an analog computation with Gaussian beams. It shows that the spatial bandwidth of the proposed differentiator is large enough such that even when the waist radius of the Gaussian beam is as narrow as ${{w}_{0}}=0.68\lambda $ ($\lambda $ is the free-space wavelength), the accuracy of the differentiator is higher than 95\%. The proposed differentiator is ultra-compact, with a thickness less than $0.1\lambda $, and useful for real-time imaging applications in THz security detections.

1.8-THz-wide optical frequency comb emitted from monolithic passively mode-locked semiconductor quantum-well laser

Mu-Chieh Lo, Robinson Guzman, Muhsin Ali, Rui Santos, Luc Augustin, and Guillermo Carpintero

Doc ID: 303924 Received 03 Aug 2017; Accepted 31 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: We report on an optical frequency comb with 14nm (~1.8 THz) spectral bandwidth at -3 dB level. It is generated using a passively mode-locked quantum-well (QW) laser in photonic integrated circuits (PICs) fabricated through an InP generic photonic integration technology platform. This 21.5-GHz colliding-pulse mode-locked laser cavity is defined by a pair of on-chip reflectors incorporating intracavity phase modulators followed by an extracavity SOA as booster amplifier. A 1.8-THz-wide optical spectrum is presented, along with an optical pulse exhibiting a width of 0.35 ps. The beat note RF spectrum has a linewidth of 450 kHz and 35-dB SNR.

Generation of Broadband Terahertz Pulses via Optical Rectification in a Chalcopyrite CdSiP₂ Crystal

Brett Carnio, Peter Schunemann, Kevin Zawilski, and Abdulhakem Elezzabi

Doc ID: 305132 Received 18 Aug 2017; Accepted 31 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: We report on the generation of broadband (0.07-6 THz) terahertz (THz) radiation via optical rectification in a <110> CdSiP2 (CSP) crystal pumped by a 50 fs, 780 nm central-wavelength optical pulse. By measuring the THz phase refractive index and the optical pump group refractive index, good phase matching can be achieved for a crystal thickness ≲200 µm. Due to this crystal’s high second order nonlinearity and low absorption losses, it is envisioned that THz generation from CSP could be further enhanced by confining the optical pump pulse to sub wavelength waveguides.

Kerr-lens mode-locked 2.3-µm Tm3+:YLF laser: a new source of femtosecond pulses in the mid infrared

Ferda Canbaz, Ismail Yorulmaz, and Alphan Sennaroglu

Doc ID: 303642 Received 31 Jul 2017; Accepted 30 Aug 2017; Posted 08 Sep 2017  View: PDF

Abstract: We report, what is to our knowledge, a new source of femtosecond pulses in the mid infrared, based on Kerr-lens mode-locked (KLM) Tm3+:YLF laser at 03 nm. An undoped ZnSe substrate was included in the resonator to provide enhanced nonlinear phase modulation during KLM operation. The Tm3+:YLF laser was end pumped with a continuous-wave Ti3+:sapphire laser at 780 nm. With 880 mW of pump power, we generated 514-fs pulses at a pulse repetition rate of 41.5 MHz with an average power of 14.4 mW. The spectral width (full width at half maximum) was measured as 15.4 nm, giving a time-bandwidth product of 0.44. We foresee that the wide availability of this gain medium as well as the straightforward pumping scheme near 800 nm will make 2.3-μm, mode-locked Tm3+:YLF lasers versatile sources of ultrashort pulses in the mid infrared.

Self-interference digital holography with geometric-phase hologram lens

KiHong Choi, Junkyu Yim, Seunghwi Yoo, and Sung-Wook Min

Doc ID: 303057 Received 28 Jul 2017; Accepted 30 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: Self-interference digital holography is actively studied because the hologram acquisition under the incoherent illumination condition is available. The key component in this system is a wavefront modulating optics, which modulates an incoming object wave into two different wavefront curvatures. In this letter, the geometric-phase hologram lens is introduced in the self-interference digital holography system, to perform as a polarization sensitive wavefront modulator, and a single-path beam splitter. This special optics has several features such as high transparency, up to 99% of modulation efficiency, thin as a few millimeters, and flat structure. The demonstration system is devised, and the numerical reconstruction results from an acquired complex hologram are presented.

Talbot Effect in Optical Lattices with Topological Charge

Jose Rodrigues, Caio Mendes, Eduardo Fonseca, and Alcenisio Silva

Doc ID: 303490 Received 27 Jul 2017; Accepted 30 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: We studied the interference resulting of the superposition of the optical lattices, which are non-diffracting fields propagating in free space, and showed a Talbot self-imaging effect. These lattices are formed by spatially Fourier transforming a “quasi”-Orbital Angular Momentum (OAM) state. We experimentally observed that although the Talbot images change, the Talbot length is insensitive to the topological charge of the “quasi”-OAM state. Our findings can be useful for laser-written photonics lattices.

Orthoscopic real-image display of digital holograms

Piotr Makowski, Tomasz Kozacki, and Weronika Zaperty

Doc ID: 300519 Received 21 Jun 2017; Accepted 30 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: We present a practical solution for the long-standing problem of depth inversion in real-image holographic display of digital holograms. It relies on a field lens inserted in front of the spatial light modulator device addressed by a properly processed hologram. The processing algorithm accounts for pixel size and wavelength mismatch between capture and display devices in a way that prevents image deformation. Complete images of large dimensions are observable from one position with a naked eye. We demonstrate the method experimentally on a 10 cm long 3D object using a single HD spatial light modulator, but it can supplement most holographic displays designed to form a real image, including circular wide angle configurations.

Edge sparsity criterion for robust holographic autofocusing

Yibo Zhang, Hongda Wang, Yichen Wu, Miu Tamamitsu, and Aydogan Ozcan

Doc ID: 302019 Received 10 Jul 2017; Accepted 30 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: Autofocusing is essential to digital holographic imaging. Previously used autofocusing criteria exhibit challenges when applied to e.g., connected objects with different optical properties. Furthermore, in earlier autofocusing criteria the polarity, i.e., whether to search for the peak or the valley as a function of depth, changes for different types of samples, which creates another challenge. Here, we propose a robust and accurate autofocusing criterion that is based on the edge sparsity of the complex optical wavefront, which we termed as the Gini index of the gradient (GoG). We demonstrated the success of GoG by imaging a wide range of objects, including resolution test targets, stained and unstained Papanicolaou smears, stained tissue sections, and blood smears.

Multilevel phase-type diffractive lens embedded in sapphire

Qian-Kun Li, Yi-Ming Lu, Jian-Guan Hua, Yanhao Yu, Lei Wang, Qi-Dai Chen, Saulius Juodkazis, and Hong-Bo Sun

Doc ID: 302048 Received 25 Jul 2017; Accepted 30 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: Herein, we report a kinoform phase-type lens (KPL), which is fabricated by femtosecond (fs-)laser induced refractive index change inside sapphire crystal. By fabricating volume phase gratings in sapphire and measuring the energy ratio of grating’s 1st and 2nd diffraction orders, the refractive index change in sapphire induced by fs-laser modification was obtained. Then a four-level KPL was designed and fabricated inside sapphire following the experimentally established scaling of refractive index change and fs-laser power. Importantly, the KPL has unique UV focusing and imaging capability as well as stable optical performance in different refractive index of environment. The KPL embedded in sapphire sustains stability of performance after a high temperature 1050℃ annealing for 30 minutes. Therefore, such KPL in sapphire has a great potential to increase the light extraction efficiency of GaN blue UV LED devices and can be used in micro-optical sensor applications for chemically harsh and high temperature environments.

The concave-lens-like long period fiber grating bidirectional high sensitivity bending sensor

Yun-Shan Zhang, Weigang Zhang, LEI CHEN, Yanxi Zhang, Song Wang, Lin Yu, Yan-Ping Li, Pengcheng Geng, Tieyi Yan, Xin-Yu Li, and Ling Xin Kong

Doc ID: 302787 Received 21 Jul 2017; Accepted 30 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: A novel bidirectional high sensitivity fiber-optic bending sensor based on the concave-lens-like long period fiber grating (CLL-LPFG) is designed and demonstrated. The CLL-LPFG is composed by an array of arc shaped grating planes and accordingly its refractive index modulation serves as a concave lens. As a result, the eigen-cladding mode of the device get closer to the device surface than the conventional counterpart. Therefore, the proposed sensor can provide a more sensitive result. The experimental results show that the bending sensitivities of the CLL-LPFG can reach -32.782 nm/m-1 within the bending range of 0-2.08 m-1, which is about 6 folds compared to the reported arts. The sensitivity can be potentially improved by optimizing the grating parameters, and especially the temperature characteristics of the CLL-LPFG can be used to manipulate the grating spectrum.

Caustic beams from unusual powers of the spectral phase

Pablo Vaveliuk, Alberto Lencina, and Oscar Martinez Matos

Doc ID: 301905 Received 11 Jul 2017; Accepted 30 Aug 2017; Posted 06 Sep 2017  View: PDF

Abstract: Caustic optical beams arising from a spectral phase whose power lies in an unusual range of values less than two are presented. Unlike what happens for conventional phase powers greater than two, it is feasible to generate caustic structures having properties that do not follow the established sorting. For instance, an asymptotic cusp caustic beam having a cusp point at infinity is demonstrated. For the sake of completeness, the caustic beam properties are analyzed within the whole real range of the phase power. Accurate behavior rules between the symmetries of the beam spectral phase and its intensity distribution are founded. These findings strengthen the fundamentals and engineering on caustic beams in diverse optical and physical branches.

Observation of polarization-maintaining light propagation in depoled compositionally disordered ferroelectrics

Mario Ferraro, Davide Pierangeli, Mariano Flammini, Giuseppe Di Domenico, Ludovica Falsi, Fabrizio Di Mei, Aharon Agranat, and Eugenio Del Re

Doc ID: 303669 Received 01 Aug 2017; Accepted 29 Aug 2017; Posted 06 Sep 2017  View: PDF

Abstract: We investigate the evolution of the state of polarization of light propagating through bulk depoled composite ferroelectrics below the Curie temperature. In distinction to standard depoled ferroelectrics, where random birefringence causes depolarization and scattering, light is observed to suffer varying degrees of depolarization and remains fully polarized when linearly polarized along the crystal principal axes. The effect is found to be supported by the formation of polarized speckles organized into a spatial lattice and occurs as the ferroelectric settles into a spontaneous super-crystal, a three-dimensional coherent mosaic of ferroelectric clusters. The polarization lattices gradually disappear as the ferroelectric state reduces to a disordered distribution of polar-nano regions above the critical point.

Polarization-independent broadband beam combining grating with measured over 98% diffraction efficiency from 10 nm to 1080nm

Junming Chen, YIBING ZHANG, Yonglu Wang, Fanyu Kong, Haopeng Huang, yanzhi wang, jin yunxia, Peng Chen, jiao xu, and jianda Shao

Doc ID: 303860 Received 01 Aug 2017; Accepted 29 Aug 2017; Posted 30 Aug 2017  View: PDF

Abstract: We report a grating solution for achieving broadband and polarization-independent properties to develop the laser combining system to much higher power levels. The grating with a high-refractive-index-contrast bilayer ridge was designed and successfully fabricated based on high power laser coatings, lithography and ion-beam etching technology. The measured −1st order non-polarized reflective diffraction efficiency of the grating exceeds 98% over the wavelength range of 1.0 -1.08μm and the highest value is 99.15%.

Dense Electro-optic Frequency Comb Generated by Two-stage Modulation for Dual-comb Spectroscopy

Wang Shuai, Xinyu Fan, Bingxin Xu, and Zuyuan He

Doc ID: 303999 Received 03 Aug 2017; Accepted 29 Aug 2017; Posted 30 Aug 2017  View: PDF

Abstract: Electro-optic frequency comb enables frequency-agile comb based spectroscopy without using sophisticated phase-locking electronics. Nevertheless, dense electro-optic frequency combs over broad spans have yet to be developed. In this work, we propose a straightforward and efficient method for electro-optic frequency comb generation with a small line spacing and a large span. This method is based on two-stage modulation: generating 18 GHz line-spacing comb at the first stage and 250 MHz line-spacing comb at the second stage. After generating an electro-optic frequency comb covering 1500 lines, we set up an easily established mutual-coherent hybrid dual-comb interferometer, which combines the generated electro-optic frequency comb and a free-running mode-locked laser. As a proof of concept, this hybrid dual-comb interferometer is used to measure the absorption and dispersion profiles of the molecular transition of H13CN with a spectral resolution of 250 MHz.

Controlled Modulation of Depolarization in Laser Speckle

Abhijit Roy, Rakesh Singh, and Maruthi Brundavanam

Doc ID: 303728 Received 01 Aug 2017; Accepted 29 Aug 2017; Posted 08 Sep 2017  View: PDF

Abstract: A new technique based on superposition of two speckle patterns is proposed and demonstrated for controlled modulation of the spatial polarization distribution of the resultant speckle. It is demonstrated both theoretically and experimentally that controlled modulation of the spatial polarization distribution of laser speckle can be achieved by proper choice of the polarization states as well as the average spatial intensity of the constituent speckles. It is shown that the proposed technique is useful to generate different speckle patterns with sinusoidal variation in their degree of polarization, which can be tuned from zero to unity. This technique can find application in sensing, biomedical studies, and in determining the rotation of an electric field vector after passing through a scattering medium.

Hybrid Non-linear Photoacoustic and Reflectance Confocal Microscopy for Label Free Subcellular Imaging with a Single Light Source

Scott Mattison, Eli Mondragon, Roland Kaunas, and Brian Applegate

Doc ID: 303191 Received 26 Jul 2017; Accepted 29 Aug 2017; Posted 08 Sep 2017  View: PDF

Abstract: Non-linear photoacoustic microscopy is capable of achieving subcellular optically resolved absorption contrast in 3-dimensions, but cannot provide structural context for the acquired images. We have developed a dual-modality imaging system which combines the optical absorption contrast of a non-linear photoacoustic microscope with the optical scattering contrast of a reflectance confocal microscope. By integrating the confocal detection optics into the optical setup of the non-linear photoacoustic microscope, the two systems were co-registered and may be acquired at the same time and with the same light source. Simultaneous images of fixed erythrocytes and fibroblasts were measured to demonstrate the complementary information that is provided by the two modalities.

3D point scanning super-resolution microscopy via polarization modulation

Cuifang Kuang, Cheng Zheng, Guangyuan Zhao, and Xu Liu

Doc ID: 303670 Received 02 Aug 2017; Accepted 28 Aug 2017; Posted 29 Aug 2017  View: PDF

Abstract: We report a new approach to achieve super-resolution in point-scanning microscopy through polarization modulation. By modulating linear polarized incident light, the emission extent of fluorescent dyes changes periodically, adding sparsity in each recording, which contributes to the super resolution reconstruction. To recover the super-resolution result from raw data, a sparse penalty based deconvolution method is implemented onto the polarization modulated dataset subsequently. By simply inserting a vortex half-wave retarder into a typical confocal microscope, we obtain the super-resolution experimental results of both Nuclear Pore complex proteins and Tubulins in Vero cells, which evidence a sub-diffraction resolution of λ/5. In addition, three-dimensional super-resolution on spatial distributed single molecules is simulated, where the significant resolution improvement in both lateral and axial directions further confirm its capacity in 3D imaging applications. Considering the no constraint on fluorescence dyes and easy implementation in point-scanning microscope, we envision the polarization modulated confocal microscope would be a helpful alternative in biological imaging.

Low-loss, broadband and high fabrication tolerant vertically tapered optical couplers for monolithic integration of Si3N4 and polymer waveguides

Jinfeng Mu, Meindert Dijkstra, Yean-Sheng Yong, Frans Segerink, Kerstin Wörhoff, Marcel Hoekman, Arne Leinse, and Sonia Garcia-Blanco

Doc ID: 296275 Received 06 Jul 2017; Accepted 28 Aug 2017; Posted 30 Aug 2017  View: PDF

Abstract: A low-loss, broadband and high fabrication tolerant optical coupler for the monolithic integration of Si3N4 and polymer waveguides is designed and experimentally demonstrated. The coupler is based on the adiabatic vertical tapering of the Si3N4 waveguides. Low-loss operation is experimentally verified at both 976 nm and 1460–1635 nm wavelengths. Measured losses per converter are as low as 0.12 dB and 0.14 dB at 976 nm and 1550 nm respectively, and below 0.2 dB at both wavelengths for lateral misalignments between the Si3N4 and polymer waveguides up to 1.0 μm.

0.85 PW laser operation at 3.3 Hz and high contrast ultra-high intensity λ=400 nm second harmonic beamline

Yong Wang, Shoujun Wang, Alex Rockwood, Brad Luther, REED HOLLINGER, Alden Curtis, Chase Calvi, Carmen Menoni, and Jorge Rocca

Doc ID: 303311 Received 26 Jul 2017; Accepted 28 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: We demonstrate the generation of 0.85 PW, 30 fs laser pulses at a repetition rate of 3.3 Hz with a record average power of 85 W from a Ti:Sapphire laser. The system is pumped by high energy Nd:glass slab amplifiers frequency doubled in LBO. Ultra-high contrast λ=400 nm femtosecond pulses were generated in KDP with > 40% efficiency. An intensity of 6.5×10^21 W/cm2 was obtained by frequency doubling 80% of the available Ti:Sapphire energy and focusing the doubled light with an f/2 parabola. This laser will enable highly relativistic plasma experiments to be conducted at high repetition rate.

Time-delay signature suppression in a chaotic semiconductor laser by fiber random grating induced random distributed feedback

Yanping Xu, Mingjiang Zhang, Liang Zhang, Ping Lu, Stephen Mihailov, and Xiaoyi Bao

Doc ID: 301557 Received 03 Jul 2017; Accepted 27 Aug 2017; Posted 06 Sep 2017  View: PDF

Abstract: We demonstrate that a semiconductor laser perturbed by distributed feedback with random time delays from a large number of scattering centers along a fiber random grating can emit light chaotically without the time-delay signature (TDS). A theoretical model is developed based on the modified Lang-Kobayashi model to numerically explore the chaotic dynamics of the laser diode subjected to random feedback. It is predicted that the random distributed feedback destroys the phase-correlated mode condition and hence suppresses the TDS. The fiber random grating is fabricated with random index modulation periods through point-by-point inscription, which introduces large numbers of phase-uncorrelated cavity modes into the semiconductor laser, leading to high dimensional chaotic dynamics and thus the concealment of the TDS. The experimentally obtained TDS value is negligible with a minimum of 0.0088, which is the smallest to date.

Closed-form expression for mutual intensity evolutionof Hermite-Laguerre-Gaussian Schell-model beams

Tatiana Alieva and Eugeny Abramochkin

Doc ID: 303385 Received 27 Jul 2017; Accepted 27 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: We derive a comprehensive closed-form expression forthe evolution of the mutual intensity (MI) of Hermite-Laguerre-Gaussian Schell-model beams (HLG-SMBs)during propagation through rotationally symmetric op-tical systems. We demonstrate that the MI of the beamassociated with a given HLG mode at any transverseplane can be presented as a linear superposition of theMIs of the SMBs associated with the equal and lowerindex modes of the same type but of complex argu-ment. The obtained expression allows easily analyzingthe evolution of the intensity distribution and the cross-correlation function of such beams and, in particular,understanding the coherence singularity formation andmodification during the beam propagation.

Spectral-temporal dynamics of high power Raman picosecond pulse using H2-filled Kagome HC-PCF

Aurélien Benoit, ekaterina ilinova, Benoit Beaudou, Benoît Debord, frederic gerome, and Fetah Benabid

Doc ID: 302147 Received 17 Jul 2017; Accepted 26 Aug 2017; Posted 29 Aug 2017  View: PDF

Abstract: We report on spectral-temporal characterization of a 1.8 µm wavelength and high-power picosecond pulse Raman source. It is generated via frequency-conversion to the 1st order Stokes of a 27 picosecond chirped-pulse Yb-doped fiber laser inside a molecular hydrogen filled Kagome hollow-core PCF. Depending on the average-power and chirp of the pump laser, the average-power of this Raman source can be as high as 9.3 W, and its pulse duration can be as short ~17 ps. In agreement with stimulated Raman scattering under the very high gain transient regime, the experimental results show the Stokes spectral structure to change following three-stage sequence when the average pump-power is increased. For a pump with a chirp corresponding to a bandwidth of 200 GHz, we found that for a pump-power lower than 7W, the Stokes spectrum is generated from the blue-side of the pump-spectrum, and then it exhibits a spectral replica of the pump-spectrum for 7-14 W pump-power range. Finally, the Stokes-spectrum is chiefly generated from the red-side of the pump-spectrum when the pump-power is increased further. Conversely, the Stokes pulse temporal profile shows a strong dependence with the pump-power. For low pump power-range, the Stokes pulse exhibits a single peak with a full-width at half maximum of ~17 ps. For higher pump powers, the Stokes pulse presents a double-peak structure with each peak having duration of less 15 ps. The present results can be used to develop compact and efficient frequency down-convertors to the increasingly widespread Yb-based picosecond lasers.

Opportunities for visible supercontinuum light generation in integrated diamond waveguides

Benjamin Feigel, David Castello-Lurbe, Hugo Thienpont, and Nathalie Vermeulen

Doc ID: 303104 Received 26 Jul 2017; Accepted 26 Aug 2017; Posted 29 Aug 2017  View: PDF

Abstract: We numerically show the advantages of using diamond-on-insulator (DOI) waveguides to design compact supercontinuum (SC) light sources for the visible (VIS) wavelength range. We conclude that the DOI platform is more suitable than silicon-nitride waveguides for tailoring the dispersion in such a way that a zero-dispersion wavelength (ZDW) is obtained in the VIS domain, as is required to achieve efficient SC generation (SCG) in this spectral range. After designing a DOI waveguide that features a ZDW at ~600 nm, we exploit it to numerically obtain a smooth SC ranging from 453 nm to 1030 nm above the -30 dB point after propagation over 4 mm. Our result goes beyond the state-of-the-art shortest VIS wavelengths induced by SCG in integrated waveguides, while using a ~26 times lower input energy and a shorter waveguide length, thus showcasing the potential of the DOI platform for on-chip VIS broadband light sources.

Mode selecting switch using multimode interference for on-chip optical interconnects

Rubana Priti, Hamed Pishvai Bazargani, Yule Xiong, and Odile Liboiron-Ladouceur

Doc ID: 300832 Received 20 Jul 2017; Accepted 25 Aug 2017; Posted 25 Aug 2017  View: PDF

Abstract: A novel mode selecting switch (MSS) is experimentally demonstrated for on-chip mode-division multiplexed (MDM) optical interconnects. The MSS consists of a Mach-Zehnder interferometer (MZI) with tapered multi-mode interference (MMI) couplers and TiN thermo-optic phase-shifters for conversion and switching between the optical data encoded on the fundamental and first order quasi-transverse electric (TE) modes. The C-band MSS exhibits >25 dB switching extinction ratio (ER) and <-12 dB crosstalk. We validate the dynamic switching with a 25.8 kHz gating signal measuring switching times for both TE0 and TE1 modes of <10.9 μs. All channels exhibit less than 1.7 dB power penalty at 10¬¹² BER while switching the NRZPRBS-31 data signals at 10 Gb/s.

Effects of ZnO layer on the structure and white light emission properties of ZnS:Mn/GaN nanocomposite system

caifeng Wang and Bo Hu

Doc ID: 302406 Received 18 Jul 2017; Accepted 25 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: ZnO films w ere inserted between the ZnS:Mn films and GaN substrates by pulsed laser deposition (PLD). The structure, morphology and optical properties of ZnS:Mn/ZnO/GaN nanocomposite systems have been investigated. X-ray diffraction (XRD) results show that there are three diffraction peaks located at 28.4°, 34.4° and 34.1°, which is corresponding to β-ZnS(111), ZnO(002) and GaN(002) plane, respectively. Due to the insertion of ZnO films, the diffraction peak intensity of ZnS:Mn in ZnS:Mn/ZnO/GaN is stronger than that of ZnS:Mn in ZnS:Mn/GaN, and the FWHM is smaller. Though the transmittance of ZnS:Mn/ZnO films is slightly lower than that of ZnS:Mn films, the transmittance is still higher than 80%. Compared with ZnS:Mn/GaN, an ultraviolet emission at 387nm (originated from the near-band emission of ZnO) and a green light emission at about 520nm appeared in the photoluminescence (PL) spectra of ZnS:Mn/ZnO/GaN, in addition to the blue emission at 435nm and the orange-red emission at 580nm. The emission at 520nm may be related to the deep-level emission from ZnO and the interface of ZnS:Mn/ZnO. The PL spectrum of ZnS:Mn/ZnO/GaN covers the visible region from the blue light to the red light (400700nm), and its color coordinate and color temperature is (0.3103,0.3063) and 6869K respectively, presenting strong white light emission.

Spectroscopic Ellipsometric Properties of Annealed Mn1.95Co0.77Ni0.28O4 Thin Films

fei zhang and Zhiming Huang

Doc ID: 302715 Received 20 Jul 2017; Accepted 25 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: Mn-Co-Ni-O thin films have important application value and their spectroscopic ellipsometric properties underwent post-annealing are still short of studies. In this paper, the visible-near infrared ellipsometric data of post-annealed Mn1.95Co0.77Ni0.28O4 (MCNO) thin films were fitted by double Lorenz, Drude and effective medium approximation (EMA) models. We found that Lorenz model can describes the small polaron oscillation and Drude model can excellently fits the conductivity produced by small polaron hopping. We got that a large number of carriers hopping between bound states under certain voltage generates a unidirectional flow of quasi free carriers which can bring about the same macroscopic properties just as free carriers in extended state and the calculated effect mass of quasi free carriers is about 150m0 (m0 is the effect mass of electron). We also found that it is mainly Lorentz oscillators and the quasi free carriers to produce the resonance absorption of electromagnetic waves in visible-near infrared waveband and both are electron absorption of lights. These results will perfect small polaron hopping theory for Mn-Co-Ni-O thin films.

Efficient Mid-infrared Laser under Different Excitation Pump Wavelengths

Jing Liu, Jie Liu, Jimin Yang, Weiwei Ma, Qinghui Wu, and Liangbi Su

Doc ID: 304912 Received 16 Aug 2017; Accepted 25 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: A laser operating at 2.8 μm in a lightly doped Er3+:SrF2 crystal is analyzed firstly for different excitation pump wavelengths: 972 nm and 1532 nm. A maximum output power of 814 mW was obtained by a 972-nm commercial laser diode (LD) and the corresponding slope efficiency was 30.4%. Laser emission under 1532 nm excitation was also achieved by efficient upconversion energy transfers. This could be an effective technique for realizing a compact and efficient upconversion laser capable of emitting in the mid-infrared regime.

Quantum delayed-choice experiment with single neutral atom

Gang Li, Pengfei Zhang, and Tiancai Zhang

Doc ID: 302840 Received 20 Jul 2017; Accepted 23 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: We present a proposal to implement quantum delayed-choice (QDC) experiment with single neutral atom, like Rubidium or Cesium atoms. In our proposal a Ramsey interferometer is adopted to observe the wave-like or particle-like behaviors of single atom depending on the existence or absence of the second $\pi/2$-rotation. A quantum-controlled $\pi/2$-rotation on target atom is realized through Rydberg-Rydberg interaction by another ancilla atom. It shows that a heavy neutral atom can also have a morphing behavior between particle and wave. The realization of QDC experiment with such heavy neutral atoms not only is significant to understand the Bohr's complementarity principle in matter-wave and matter-particle domain but also have great potential on quantum information process with neutral atoms.

Burst-mode thulium all-fiber laser delivering femtosecond pulses at a 1-GHz intra-burst repetition rate

Parviz Elahi, Hamit Kalaycioglu, Onder Akcaalan, Cagri Senel, and F Omer Ilday

Doc ID: 300574 Received 23 Jun 2017; Accepted 23 Aug 2017; Posted 25 Aug 2017  View: PDF

Abstract: We report on the development of what we believe to be the first ultrafast burst-mode laser system operating at a central wavelength of approximately 2 μm, where water absorption and consequently absorption of most biological tissue is very high. The laser comprises a harmonically mode-locked 1-GHz oscillator, which, in turn, seeds a fiber amplifier chain. The amplifier produces 500-ns long bursts containing 500 pulses with a 1-GHz intra-burst and 50-kHz inter-burst repetition rates, respectively at an average power of 1 W, corresponding to 40 nJ pulse and 20 μJ burst energies, respectively. The entire system is built in an all-fiber architecture and implements dispersion management such that output pulses are delivered directly from a single-mode fiber with a duration of 340 fs and without requiring any external compression. This GHz-repetition rate system is intended for ablation-cooled laser material removal in the 2 μm wavelength region, which is particularly interesting for laser surgery due to the exceptionally high tissue absorption at this wavelength.

Design of Structured YAG:Ce Scintillators with Enhanced Outcoupling for Image Detection in the Extreme Ultraviolet

Lukas Bahrenberg, Stefan Herbert, Tobias Mathmann, Serhiy Danylyuk, Jochen Stollenwerk, and Peter Loosen

Doc ID: 302710 Received 24 Jul 2017; Accepted 23 Aug 2017; Posted 06 Sep 2017  View: PDF

Abstract: In this Letter, the authors present a design study on YAG:Ce scintillator plates with a microstructured and coated surface. The goal of the study is to improve the outcoupling efficiency and to optimize the directionality of the scintillation light with respect to indirect image detection in the extreme ultraviolet spectral range (5 - 50 nm wavelength). In a geometric optical simulation, a gain in outcoupling efficiency by over a factor of four is shown while the directionality of the scintillation light is improved with respect to state-of-the-art plane scintillator plates.

Fair Comparison of Complexity between Multi-band CAP and DMT for Data Center Interconnects

Jinlong Wei, Christian Sánchez, and Elias GIACOUMIDIS

Doc ID: 297069 Received 31 May 2017; Accepted 21 Aug 2017; Posted 22 Aug 2017  View: PDF

Abstract: We present the first known detailed analysis and fair comparison of complexity of 56-Gb/s Multi-band CAP and DMT over 80-km DCF-free SMF links based on intensity modulation and direct detection (IMDD) for data center interconnects. We show that the matched FIR filters and (I)FFT take the majority of the complexity of the Multi-band CAP and DMT, respectively. Choice of the multi-band CAP sub-band count and the DMT (I)FFT size makes significant impact to system complexity or performance and trade-off must be considered.

Ag nanowire-assisted low threshold WGM lasing from polymer fiber

suneetha sebastian, M Kailasnath, V Nampoori, and Asokan S

Doc ID: 295488 Received 09 Jun 2017; Accepted 20 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: Well resolved Whispering Gallery Mode (WGM) emission has been observed from dye doped polymer optical fiber laser with Ag nanowires in the micro cavity. Low threshold lasing emission with high photostability of the active medium has been noticed with a given concentration of Ag nanowires in the fiber as compared to bare dye doped polymer fiber. Quantum yield and lifetime measurements of the dye (active medium) with and without nanowires confirms that presence of nanowires enhance the rate of radiative decay of the dye molecules thereby providing low pump pulse energy for the excitation of lasing modes in the fiber cavity.

Babinet’s principle for mutual intensity

Sergey Sukhov, Mahed Batarseh, Roxana Rezvani Naraghi, Heath Gemar, alexandru tamasan, and Aristide Dogariu

Doc ID: 300929 Received 26 Jun 2017; Accepted 18 Aug 2017; Posted 25 Aug 2017  View: PDF

Abstract: In classical diffraction theory, the Babinet’s principle relates the electromagnetic fields produced by complementary sources. This theorem was always formulated for single-point quantities, both intensities or field amplitudes, in conditions where the full spatial coherence is implicitly assumed. However, electromagnetic fields are, in general, partially coherent and their spatial properties are described in terms of two-point field-field correlation functions. In this case, a generalized Babinet’s principle can be derived that applies to the spatial coherence functions. We present both the derivation and the experimental demonstration of this generalized Babinet theorem.

Single Silicon CMOS platform for multi-spectral detection from THz to X-rays

Mostafa Shalaby, Carlo Vicario, and Christoph Hauri

Doc ID: 295247 Received 12 May 2017; Accepted 11 Aug 2017; Posted 24 Aug 2017  View: PDF

Abstract: Charge coupled devices (CCDs) is a well-established imaging concept in the visible and x-ray frequency ranges. However, the small quantum photon energies of terahertz (THz) radiation have hindered the use of this mature semiconductor technological platform in this frequency range, leaving THz imaging totally dependent on low-resolution bolometer technologies. Recently, it was shown that silicon CCDs can detect THz photons under special conditions but the detection sensitivity was limited. Here we show that silicon CMOS technology offers enhanced detection sensitivity of almost two orders of magnitude compared to CCDs. Our findings allow us to extend the low frequency THz cut off to less than 2 THz nearly closing the technological gap with electronic imagers operating up to 1 THz. Furthermore, with the CMOS technology being sensitive to mid infrared (midIR) and the x-ray ranges, we demonstrate multispectral detection with a single detector from 1 Exahertz to 2 THz. This overcomes the present challenge in spatially overlapping THz/midIR pump and x-ray probe radiation at facilities like free electron lasers, synchrotron and laser-based x-ray sources.

175 nm period grating fabricated by i-line proximity mask-aligner lithography

yannick bourgin, Daniel Voigt, Thomas Käsebier, Thomas Siefke, Ernst-Bernhard Kley, and Uwe Zeitner

Doc ID: 300876 Received 26 Jun 2017; Accepted 07 Aug 2017; Posted 29 Aug 2017  View: PDF

Abstract: We report the fabrication of periodic structures with a critical dimension of 90 nm on a fused silica substrate by i-line (=365nm) proximity mask-aligner lithography. This realization results from the combination of the improvements of the optical system in the mask-aligner (known as MO Exposure Optics), short period phase-mask optimization, and the implementation of self-aligned double patterning (SADP). A 350 nm period grating is transferred into a sacrificial polymer layer and coated with an aluminum layer. The removing of the metal initially present on the horizontal surfaces and on top of the polymer grating, leave a 175 nm period grating on the wafer, which can be used as wire grid polarizer. A computation of the efficiency is performed from the measured profile and confirms the deep-blue visible to infra-red operation range.

Atmospheric Boundary layer CO2 remote sensing with a direct detection LIDAR instrument based on a widely tunable optical parametric source

Erwan Cadiou, Dominique Mammez, Jean-Baptiste Dherbecourt, Guillaume Gorju, Jacques Pelon, Jean-Michel Melkonian, Antoine Godard, and Myriam Raybaut

Doc ID: 302785 Received 18 Jul 2017; Accepted 07 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: We report on the capability of a direct detection differential absorption lidar (DIAL) for range resolved and integrated path (IPDIAL) remote sensing of CO2 in the atmospheric boundary layer (ABL). The laser source is an amplified nested cavity Optical Parametric Oscillator (NesCOPO) emitting about 8 mJ at the two measurement wavelengths selected near 2050 nm. Direct detection atmospheric measurements are taken from the ground using a 30 Hz frequency switching between emitted wavelengths. Results show that comparable precision measurements are achieved in DIAL and IPDIAL modes (not better than a few ppm) on high SNR targets such as near range ABL aerosol and clouds, respectively. Instrumental limitations are analysed and degradation due to cloud scattering variability is discussed to explain observed DIAL and IPDIAL limitations.

Study on focusing of subwavelength imaging of point source based on two-dimensional photonic crystals

liang ming, Ma Liang, Songlin Zhuang, Jinke Niu, and Jiabi Chen

Doc ID: 298223 Received 20 Jun 2017; Accepted 25 Jul 2017; Posted 07 Sep 2017  View: PDF

Abstract: A new focusing structure based on two-dimensional (2D) photonic crystal (PC) with the negative refraction and subwavelength imaging characteristics is proposed, consisting of periodic array air holes in silicon. The light radiated from a point source can form a subwavelength imaging of which half-width reaches 0.47λ through a wedge PC. Due to the influence of the phase difference and evanescent field, the symmetry plane of the image is inside the structure rather than the boundary. In addition, moving the PC by 2μm to the left horizontally, the image moves by 3.57μm, and the half-width of each image is less than the half of wavelength in this process.

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