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Controlled-phase manipulation module for orbital-angular-momentum photon states

Fang-Xiang Wang, Juan Wu, Wei Chen, Zhen-Qiang Yin, Shuang Wang, Guang-can Guo, and Zhengfu Han

Doc ID: 312853 Received 07 Nov 2017; Accepted 15 Dec 2017; Posted 15 Dec 2017  View: PDF

Abstract: Phase manipulation is essential to quantum information processing, for which the orbital angular momentum (OAM) of photon is a promising high-dimensional resource. Dove prism (DP) is one of the most important element to realize the nondestructive phase manipulation of OAM photons. DP usually changes the polarization of light and thus decreases the purity of a spin-OAM hybrid state. DP in a Sagnac interferometer also introduces an mode-dependent global phase to the OAM mode. In this work, we implemented a high-dimensional controlled-phase manipulation module (PMM), which can compensate the mode-dependent global phase and thus preserve the purity of the spin-OAM state. The PMM is stable for free running and is suitable to realize the high-dimensional controlled-phase gate for spin-OAM hybrid states.

Tunable coupling of spin ensembles

Feng-Yang Zhang and Chui-Ping Yang

Doc ID: 313064 Received 09 Nov 2017; Accepted 14 Dec 2017; Posted 15 Dec 2017  View: PDF

Abstract: Spin ensembles are promising candidates for quantum memory units because they have long coherence time. Controlling the coupling between spin ensembles is necessary and important in quantum information processing. In this letter, we propose a method to realize tunable coupling between spin ensembles by a superconducting flux qubit acting as a coupler. The resulting coupling can be used to high-fidelity speed up adiabatic transfer of quantum information.

Spectral responses of linear grating filters under full-conical incidence

Wei Wang, Xumin Gao, xiangfei Shen, zheng shi, and yongjin wang

Doc ID: 313339 Received 13 Nov 2017; Accepted 14 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: To completely clarify the spectral responses of linear grating filters (LGFs) under full-conical incidence (where the incident plane is parallel to the linear grating bars), a bandstop LGF is implemented on an HfO2-on-silicon platform, and its spectral responses are comprehensively investigated. The measured spectra agree well with the simulated outcomes. For the TM- (or TE-) polarized wave under full-conical incidence, there exist a pair of resonance bands, whose spectral features differ significantly from each other. One resonance band has a high angular tolerance and is capable of accommodating divergent waves, whereas the other band presents a tunable spectral linewidth and can be used to achieve an ultra-high Q factor. In particular, it is demonstrated that all of the resonance bands under full-conical incidence are degenerate regardless of what the value of the incident angle is. Our investigations reveal interesting spectral attributes of LGFs under full-conical incidence, which are highly beneficial for developing new filtering devices.

Strategies for achieving intense single-cycle pulses with in-line post-compression setups

Francisco Silva, Benjamín Alonso, Warein Holgado, Rosa Romero, Julio San Roman, Enrique Conejero Jarque, Hans Koop, Vladimir Pervak, Helder Crespo, and Íñigo Sola

Doc ID: 313694 Received 20 Nov 2017; Accepted 14 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: Intense few- and single-cycle pulses are a powerful tool in different fields of science. Nowadays, third- and higher-order terms in the remnant spectral phase of the pulses remain a major obstacle for obtaining high-quality few- and single-cycle pulses from in-line post-compression setups. In the present work, we show how input pulse shaping can be successfully applied to standard post-compression setups to minimize the occurrence of high-order phase components during nonlinear propagation and to directly obtain pulses with durations down to 3 fs. Furthermore, by combining this pulse shaping of the input pulse with new-generation broadband chirped mirrors and material addition for remnant third-order phase correction, single-cycle 2. fs pulses can be routinely obtained from in-line configurations.

An integrated Raman laser operating in the near-visible

Pawel Latawiec, Vivek Venkataraman, amirhassan shams-ansari, Matthew Markham, and Marko Loncar

Doc ID: 313345 Received 13 Nov 2017; Accepted 13 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: Integrated visible photonic devices will forge the backbone of next-generation optical technologies, as evidenced by recent demonstrations in sensing and quantum optics. Synthetic single crystal diamond, a high-index material with a transparency window spanning the UV, visible, infrared, and beyond, hosts single-photon-emitting defects and bulk nonlinear properties which make these advances possible. Using a high-Q diamond microresonator (Q > 300,000) interfaced with high-power-handling directly-written doped-glass waveguides, we demonstrate a Raman laser in an integrated platform pumped in the near-visible. Both TM-to-TE and TE-to-TE lasing is observed, with a Raman lasing threshold as low as 20 mW and Stokes power of over 1 mW. Stokes emission is tuned over a 150 nm (60 THz) bandwidth around 875 nm wavelength, corresponding to 17.5% of the center frequency.

An Angle-Insensitive Amorphous Silicon Optical Filter for Fluorescence Contact Imaging

Efthymios Papageorgiou, Hui Zhang, Bernhard Boser, Catherine Park, and Mekhail Anwar

Doc ID: 308577 Received 09 Oct 2017; Accepted 13 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: We introduce a novel amorphous silicon absorption filter that has high rejection for all angles of incident light for wavelengths below approximately 700 nm. This filter is used for microscopic cancer tissue detection in a small intraoperative contact fluorescence imaging system that requires excitation light at oblique angles. Our 15 μm thick filter presents over five orders of magnitude rejection at 633 nm, making it compatible with several clinically-tested fluorophores, including IR700DX. We have demonstrated imaging of fluorescently-labeled human HER2+ breast cancer tissue using the filter and we can reliably detect microscopic clusters of breast cancer cells with only a 75 ms integration time.

Fiber-facet integrated guided-mode resonance filters and sensors: Experimental realization

Hafez Hemmati, Yeong Ko, and Robert Magnusson

Doc ID: 309003 Received 11 Oct 2017; Accepted 13 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: Guided-mode resonant (GMR) thin films integrated on fiber tips are known to realize compact filters and sensors. However, limited progress in experimental realization has been reported to date. Here, we provide a considerable advance in this technology as we experimentally demonstrate efficient fiber-facet mounted device prototypes. To retain a large aperture for convenient coupling, we design and fabricate silicon-nitride-based resonators on the tip of a multimode fiber. We account for light propagation along the multimode fiber with exact numerical methods. This establishes the correct amplitude and phase distribution of the beam incident of the tip-mounted GMR element thus enabling us to properly predict the resonance response. To fabricate the integrated GMR structures on the tips of fibers, we employ standard microfabrication processes including holographic interference lithography and reactive-ion etching. The experimental results agree with simulation with an example device achieving high efficiency of ~77% in transmission. To investigate fiber sensor operation, an etched silicon nitride fiber-tip filter is surrounded with solutions of various refractive indices yielding an approximate sensitivity of 200 nm/RIU.

Fabricate nanogap-rich plasmonic nanostructures through an optothermal surface bubble in a droplet

Farzia Karim, Erick Vasquez, and Chenglong Zhao

Doc ID: 309712 Received 24 Oct 2017; Accepted 13 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: A rapid and cost-effective method for the fabrication of nanogap-rich structures is demonstrated in this work. The method utilizes the Marangoni convection around an optothermal surface bubble inside a liquid droplet with a nanoliter volume. The liquid droplet containing metallic nanoparticles reduces the sample consumption and confines the liquid flow. The optothermal surface bubble creates a strong convective flow that allows for the rapid deposition of the metallic nanoparticles to form nanogap-rich structures on any substrate under ambient conditions. This method will enable a broad range of applications such as biosensing, environmental analysis, and nonlinear optics.

Two-color interpolation of absorption response for quantitative Acousto-Optic imaging

Maïmouna Bocoum, Jean-Luc Gennisson, Caroline Venet, Mingjun Chi, Paul Petersen, Alexander Grabar, and Francois Ramaz

Doc ID: 310205 Received 30 Oct 2017; Accepted 13 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: Diffuse Optical Tomography (DOT) is a reliable and widespread technique for monitoring qualitative changes in absorption inside highly scattering media. It has been shown, however, that Acousto-Optic (AO) imaging can provide significantly more qualitative information, without the need for inversion algorithms, due to the spatial resolution afforded by ultrasound probing. In this article, we show how, by using multiple-wavelength AO imaging, it is also possible to perform quantitative measurements of absorber concentration inside scattering media.

On-chip arbitrary RF photonic filter with algorithm-driven reconfigurable resolution

Hengyun Jiang, Lianshan Yan, and David Marpaung

Doc ID: 310061 Received 26 Oct 2017; Accepted 12 Dec 2017; Posted 13 Dec 2017  View: PDF

Abstract: Integrated microwave filter that can precisely manipulate the spectrum of analog signals over a wide bandwidth, is highly desired for signal processing in radio frequency systems. All photonic programmable microwave filters to date have been limited by the trade-off between the resolution and the operation bandwidth to construct arbitrary filter shapes. Here, we propose a new approach to synthesize RF photonic filter with an arbitrary response and reconfigurable resolution through phase-only tailoring which is implemented in a low-loss photonic chip. Based on an algorithm incorporating the target transfer function of the filter, the optimal one or multiple resolutions can be intelligently chosen by tuning the coupling coefficients and the round-trip phase of cascaded ring resonators. The reconfigurable resolution could be as high as 300MHz over a wide bandwidth of 25GHz in our experiments. The result points out a new conception to create a high-performance programmable filter.

Mid-infrared supercontinuum generation from 1.6 to >11μm using concatenated step-index fluoride and chalcogenide fibers

Ramon Martinez, Genevieve Plant, Kaiwen Guo, Brian Janiszewski, Michael Freeman, Robert Maynard, Mohammed Islam, Fred Terry, Oseas Alvarez, Francois Chenard, Robert Bedford, Ricky Gibson, and Agustin Ifarraguerri

Doc ID: 310053 Received 02 Nov 2017; Accepted 12 Dec 2017; Posted 12 Dec 2017  View: PDF

Abstract: We demonstrate an all fiber supercontinuum laser that generates a continuous spectrum from 1.6µm to >11µm with 417mW on time average power at 33% duty cycle. By utilizing a master oscillator power amplifier pump with three amplification stages and concatenating solid core ZBLAN, arsenic sulfide, and arsenic selenide fibers, we shift 1550nm light to ~4.5µm, ~6.5µm, and >11μm, respectively. With 69mW past 7.5µm, this source provides both high power and broad spectral expansion, while outputting a single fundamental mode.

Fully digital programmable optical frequency comb generation and application

Xianglei Yan, Xihua Zou, Wei Pan, Lianshan Yan, and Jose Azana

Doc ID: 310129 Received 30 Oct 2017; Accepted 11 Dec 2017; Posted 12 Dec 2017  View: PDF

Abstract: We propose a fully digital programmable OFC generation scheme based on binary phase-sampling modulation, wherein an optimized bit sequence is applied to phase modulate a narrow-linewidth light wave. Programming the bit sequence enables to tune both the comb spacing and comb-line number (i.e., number of comb lines). The programmable OFCs are also characterized by ultra-flat spectral envelope, uniform temporal envelope and stable bias-free setup. Target OFCs are digitally programmed to have 19, 39, 61, 81, 101 or 201 comb lines and to have a 100, 50, 20, 10, 5 or 1 MHz comb spacing. As an application, a scanning-free temperature sensing system using a proposed OFC with 1,001 comb lines was also implemented with a sensitivity of 0.89ºC/MHz.

Backscatter Particle Image Velocimetry via Optical Time-of-flight Sectioning (PIVOTS)

Megan Paciaroni, Yi Chen, Kyle Lynch, and Daniel Guildenbecher

Doc ID: 309090 Received 19 Oct 2017; Accepted 11 Dec 2017; Posted 12 Dec 2017  View: PDF

Abstract: Conventional particle image velocimetry (PIV) configurations require a minimum of two optical access ports, inherently restricting the technique to a limited class of flows. Here, the development and application of a novel method of backscattered time-gated PIV requiring a single optical access port is described along with preliminary results. The light backscattered from a seeded flow is imaged over a narrow optical depth selected by an optical Kerr effect (OKE) time gate. The picosecond duration of the OKE time gate essentially replicates the width of the laser sheet of conventionalPIV by limiting detected photons to a narrow time-of-flight within the flow. Thus, scattering noise from outside the measurement volume is eliminated. This PIV via Optical Time-of-flight Sectioning (PIVOTS) technique can be useful in systems with limited optical access and in flows near walls or other scattering surfaces.

In-fiber high-speed recognition of incoherent-light broadband energy-spectrum patterns

Jeonghyun Huh and Jose Azana

Doc ID: 312469 Received 31 Oct 2017; Accepted 11 Dec 2017; Posted 12 Dec 2017  View: PDF

Abstract: A fiber-optics system is proposed and experimentally demonstrated for real-time, on-the-fly identification of an incoherent-light energy-spectrum pattern based on dispersion-induced time-spectrum convolution. In the proposed system, the incoming frequency-spectrum patterns to be identified are modulated by a time-mapped version of the target intensity profile. Following propagation through a suitable fiber-optics dispersive medium, the measured output temporal waveform provides a correlation of the incoming spectra with the programmed target pattern. This enables direct, real-time detection of the matching energy spectra, without any further numerical post-processing. We experimentally demonstrate successful recognition of a target infrared spectral pattern, extending over a bandwidth of 1.5 THz with a resolution of ~12 GHz, with sub-MHz update rates. A path for further performance improvements is also suggested.

Nanoscale Beam Splitters Based on Gradient Metasurfaces

Di Zhang, Mengxin Ren, Wei Wu, Ninghui Gao, Xuanyi Yu, Wei Cai, Xinzheng Zhang, and Jingjun Xu

Doc ID: 312993 Received 08 Nov 2017; Accepted 11 Dec 2017; Posted 12 Dec 2017  View: PDF

Abstract: Beam splitters are essential components in various optical and photonic applications, for example, interferometers, multiplexers, and so on. Present beam splitters based on cubes or plates are normally bulky. Realizing beam splitters in nano scales is useful to reduce the total size of photonic devices. We demonstrate here a beam splitter with nanoscale thickness based on a gradient metasurface comprising lithium niobate cylinder arrays. Since one unit cell of metasurface comprising two cylinder rows showing two opposite phase gradients, the incident light is split into different directions according to the generalized Snell's law. The split ratio is proved to be effectively tunable.

Accurate terahertz spectroscopy of supported thin films by precise substrate thickness correction

Keno Krewer, Zoltan Mics, Jacek Arabski, Guy Schmerber, Eric Beaurepaire, Mischa Bonn, and Dmitry Turchinovich

Doc ID: 307052 Received 11 Oct 2017; Accepted 11 Dec 2017; Posted 13 Dec 2017  View: PDF

Abstract: We present a new approach for accurate terahertz time-domain spectroscopy of thin films deposited on dielectric substrates. Our approach relies on the simultaneous measurement of film and substrate, allowing for 15 nm - precise determination of the thickness variation between sample and reference. Our approach allows for unprecedentedly accurate determination of the terahertz conductivity of the thin film. We demonstrate our approach on a 10 nm - thin iron film deposited on a 500 μm MgO substrate. We determine the Drude momentum relaxation time in iron to within 0.15 fs uncertainty.

Giant visible and infrared light attenuation effect in nanostructured narrow-bandgap glasses

Roman Holovchak, Yaroslav Shpotyuk, Jakub Szlęzak, Andrzej Dziedzic, Adam Ingram, and Joseph Cebulski

Doc ID: 313234 Received 13 Nov 2017; Accepted 11 Dec 2017; Posted 15 Dec 2017  View: PDF

Abstract: A unique effect of Bi on the optical and electrical properties of mixed Ga-containing Ge-Se and Ge-Te glasses is discovered. It is shown that glass with low Bi content is completely transparent in 3-16 um spectral range, while the glass with slightly higher Bi content possesses a large (>10 db/mm) attenuation coefficient, making a ~mm thick glass sample fully opaque to VIS-IR radiation. Despite of this contrast, both types of glasses are found to retain their semiconducting properties, the DC conductivity at room temperature, ~ 10^-3 S/m, being comparable to that of silicon.

The role of symmetry in modes coupling in twisted microstructured optical fibers

Maciej Napiórkowski and Waclaw Urbanczyk

Doc ID: 313626 Received 23 Nov 2017; Accepted 11 Dec 2017; Posted 15 Dec 2017  View: PDF

Abstract: We have studied the effect of symmetry on coupling between core and cladding modes in helical microstructured fibers, which gives rise to resonant loss peaks observed in the fiber transmission spectra. We demonstrate that the selection rules for orbital and spin angular momenta of coupled modes, proposed first for twisted conventional fibers, have universal character and correctly identify the coupled cladding modes in helical MOFs. Moreover, we show for the first time the effect of coupling between the modes of opposite polarization handedness in twisted MOFs.

Nonlinear Refractive Index Measurements Using Time-Resolved Digital Holography

Balys Momgaudis, Stephane Guizard, Allan Bilde, and Andrius Melninkaitis

Doc ID: 308416 Received 04 Oct 2017; Accepted 11 Dec 2017; Posted 12 Dec 2017  View: PDF

Abstract: In this paper a novel method to evaluate nonlinear refractiveindex using time-resolved digital holographicmicroscopy is introduced. To demonstrate the viabilityof the method cross - correlative nonlinear refractive indexvalues for sapphire are measured experimentally:2.75·10-20 m^2/W at 1030 nm and 4.10·10-20 m^2/W 515 nmwavelengths. Obtained results for sapphire are comparedto those available in literature obtained by othermethods.

Quantum Anomalous Hall-Quantum Spin Hall Effect in one-dimensional optical superlattices

Ce Shang, Xianfeng Chen, weidong luo, and Fangwei Ye

Doc ID: 312961 Received 07 Nov 2017; Accepted 10 Dec 2017; Posted 11 Dec 2017  View: PDF

Abstract: We consider the topological characteristics of the spin-orbital coupling particles loaded in a one-dimensional( 1D) optical superlattices subject to theZeeman field. The phase shift of the superlattice provides a virtual dimension which allows us to simulate two-dimensional (2D) topological phases with a physically 1D system. The system possess a variety of quantum phase transitions over a large parametric space, and two important topological phases, namely, quantum anomalous Hall (QAH) and quantum spin Hall(QSH) phase are found to coexist in the system, but they reside in different bandgaps. This new category of gap-dependent quantum anomalous Hall-quantum spin Hall insulator, paves the way for the possible observationof the coexistence of QSH and QAH effect at one platform.

Optothermal control of gains in erbium-doped whispering-gallery microresonators

Liu Xiaofei, Tie-Jun Wang, and Chuan Wang

Doc ID: 312966 Received 07 Nov 2017; Accepted 10 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: Erbium-doped whispering-gallery microcavities have great potentials in many important applications, such as precision detection and microcavitylasers. However, they are sensitive to the fluctuations from the pump laser and the environment. Here we demonstrate the precise controlling oftransmission spectrum and optical gains using optothermal scanning methods in erbium-doped whispering-gallery microcavities. The probe signalcan exhibit transitions between asymmetric Fano-like resonances and Lorentz peak (or dip) through tuning its input frequency and the scanningspeed of the pump laser. In particular, the analytical calculations based on laser rate equations can fit well with experimental results through adiabatically eliminating the anticlockwise optical mode. Our work show that the optothermal control of gains is more robust to external noises, which paves a crucial step toward the application in the ultra-sensitive detection.

Direct laser writing combined with a phase-delay probe

Shaobei Li, Chao Liang, Feifei Li, Lihong shi, Chengwei Du, bolin fan, Xuliang Wang, Zhitao Zan, Hongjian Chen, and Wenbo Yan

Doc ID: 313088 Received 08 Nov 2017; Accepted 09 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: We develop on lithium niobate crystals a photorefractive direct-laser-writing approach, in which we combine in one beam both direct writing and phase-delay probing functionalities to extract the in-situ information of the refractive index or the electrostatic field. The phase-delay signal, predicted well by the photorefractive theory, is used as a feedback for tuning the exposure time or scanning speed of the focused laser, in order to control the refractive index change (Δn) at single points and scanning lines. Different features found in creating Δn at the points and lines are explained by the different photorefractive response in the two cases.

Interpreting angular momentum transfer between electromagnetic multipoles using vector spherical harmonics

Garth Jones and Roger Grinter

Doc ID: 308534 Received 03 Oct 2017; Accepted 09 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: The transfer of angular momentum between a quadrupole emitter and a dipole acceptor is investigated theoretically. Vector spherical harmonics are used to describe the angular part of the field of the mediating photon. Analytical results are presented for predicting angular momentum transfer between the emitter and absorber, within a quantum electrodynamical framework. We interpret the allowability of such a process, which appears to violate conservation of angular momentum, in terms of the breakdown of the isotropy of space at the point of photon absorption (detection). This is consistent with Noether’s Theorem and demystifies some common misconceptions about the nature of the photon. The results have implications for interpreting the detection of photons from multipole sources and offers insight into limits on information that can be extracted from quantum measurements in photonic systems.

An efficient 1.7 m light source based on KTA-OPO derived by Nd:YVO4 self-Raman laser

Haiyong Zhu, Junhong Guo, Yanmin Duan, Jing Zhang, Yongchang Zhang, Changwen Xu, hongyan wang, and Dianyuan Fan

Doc ID: 309990 Received 26 Oct 2017; Accepted 09 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: An intra-cavity optical parametric oscillator (OPO) emitting at 1.7 μm derived by Nd:YVO4 self-Raman laser was demonstrated with a KTiOAsO4 (KTA) crystal used as nonlinear optical crystal. An laser diode end pumped acousto-optic Q-switched Nd:YVO4 self-Raman laser at 1176 nm was employed as the pump source. At an incident pump power of 12.1 W and a pulse repetition frequency of 60 kHz, average output power up to 1.2 W signal light at 1742 nm was obtained, with the diode to signal conversion efficiency of 10%. The pulse width was about 11 ns and spectral line-width was less than 0.5 nm for the signal light. The results show that compact intra-cavity KTA-OPO derived by Nd:YVO4 self-Raman laser was an efficient way for 1.7 μm waveband laser generation and owns potential application in biological imaging, laser therapy, special materials processing , etc.

Improved 2 x 2 Mach-Zehnder switching using coupled-resonator photonic-crystal nanobeams

Joshua Hendrickson, Richard Soref, and Ricky Gibson

Doc ID: 310136 Received 27 Oct 2017; Accepted 09 Dec 2017; Posted 12 Dec 2017  View: PDF

Abstract: Design and simulation results are presented for an on-chip 2 × 2 Mach-Zehnder-based optical switch where each arm of the interferometer is composed of a coupled-resonator optical waveguide. The individual resonators are one-dimensional photonic crystal nanobeam cavities and switching occurs through thermally induced changes in the refractive index of the silicon structure using integrated heating pads. The performance of the coupled resonator device is directly compared to its single resonator counterpart and significant improvement is found in the bar-state crosstalk metric.

4.24 μm mid-infrared laser based on a single Fe2+ doped ZnSe microcrystal

Shenyu Dai, Guoying Feng, Hong Zhang, Shougui Ning, Yao Xiao, and Shouhuan Zhou

Doc ID: 312831 Received 06 Nov 2017; Accepted 09 Dec 2017; Posted 12 Dec 2017  View: PDF

Abstract: In this letter, we report the first time a micron-sized mid-infrared Fe2+:ZnSe laser based on a single microcrystal. Typical laser emissions centering at 4.24 μm are observed from a selected Fe2+-doped ZnSe microcrystal under 2.94 μm excitation of Er:YAG laser at room temperature. The laser linewidth is ~10 nm, pulse width is ~50 ns and the lasing threshold is ~7.4 mJ/pulse. The lasing wavelength is stable as the pump energy increases and is consistent with the strong absorption position of carbon dioxide in the atmosphere.

High-charge and multiple optical vortex coronagraphy from single-stage spin-orbit arithmetics

Etienne Brasselet and Artur Aleksanyan

Doc ID: 308903 Received 12 Oct 2017; Accepted 09 Dec 2017; Posted 12 Dec 2017  View: PDF

Abstract: Since five years, so-called optical vortex phase masks have been installed on many ground-based large telescopes in the framework of high-contrast astronomical imaging development. To date, such instrumental advances have been restricted to the use of helical phase masks of the lowest even order, essentially due to design and manufacturing difficulties. Here we propose a single-stage on-axis scheme to realize higher-order vortex coronagraphs based on already optimized helical phase masks with topological charge two. By extending our approach to an off-axis design, we also explore the implementation of multiple-star vortex coronagraphy. Experimental laboratory demonstration is reported and supported by numerical simulations. These results offer a practical roadmap to the realization of future coronagraphic tools with enhanced performances.

Optically induced transparency in bosonic cascade lasers

Timothy Liew and Alexey Kavokin

Doc ID: 308220 Received 29 Sep 2017; Accepted 07 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: Bosonic cascade lasers are terahertz (THz) lasers based on stimulated radiative transitions between bosonic condensates of excitons or exciton-polaritons confined in a trap. We study the interaction of an incoming THz pulse resonant in frequency with the transitions between neighboring energy levels of the cascade. We show that at certain optical pump conditions the cascade becomes transparent to the incident pulse: it neither absorbs nor amplifies it, in the mean field approximation. The populations of intermediate levels of the bosonic cascade change as the THz pulse passes, nevertheless. In comparison, a fermionic cascade laser does not reveal any of these properties.

Cavity-birefringence-dependent h-shaped pulse generation in a thulium-holmium doped fiber laser

Junqing Zhao, Lei Li, Luming Zhao, Dingyuan Tang, and Deyuan SHEN

Doc ID: 313173 Received 09 Nov 2017; Accepted 07 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: We report on a type of 2 μm h-shaped pulse generation in a thulium-holmium doped fiber laser, for the first time to the best of our knowledge, and also first experimentally investigate its cavity birefringence and pump power dependences. The pulsed operation is achieved by using an asymmetric nonlinear optical loop mirror (NOLM). ~52.7 m dispersion-shifted fiber and ~3.8 m ultra-high numerical aperture fiber are incorporated into the NOLM to increase its nonlinear effect. The h-shaped pulse shows both polarization state (PS) and pump power dependences even when only fibers with randomly weak birefringence are employed. By further incorporating different lengths of high birefringence polarization-maintaining fiber (PMF), i.e introducing different amounts of linear cavity birefringence, consequently much larger pulse tuning ranges can be realized. Especially when the PMF is lengthened to ~2.3 m, through tuning the PS the achieved longest pulse duration (~318.14 ns) can almost cover the whole repetition period (~3 .96 ns), corresponding to a pulse duty circle of ~98.2%, the largest ever reported from a fiber laser to the best of our knowledge. We demonstrate the related characteristics in detail.

Wavelength-tunable high-order Hermite-Gaussian modes and OAM-tunable vortex beam in dual-off-axis pumped Yb:CALGO laser

Yijie Shen, Yuan Meng, Xing Fu, and Mali Gong

Doc ID: 312834 Received 06 Nov 2017; Accepted 07 Dec 2017; Posted 07 Dec 2017  View: PDF

Abstract: A dual-off-axis pumping scheme is presented to generate wavelength-tunable high-order Hermite-Gaussian (HG) modes in Yb:CaGdAlO4 (Yb:CALGO) lasers. The mode and wavelength can be actively controlled by the off-axis displacements and pump power without any supplementary intracavity elements. The purities of the output HG modes are quantified by intensity distributions and the measured M2 values. The highest order reaches m = 15 for stable HGm,0 mode and wavelengthtunable width is about 10 nm. Moreover, through externally converting the HGm,0 modes, the vortex beams with a large OAM-tunable range form ±1 to ±15 is produced. This work is effective for largely scaling the spectral and OAM tunable ranges of vortex beams.

Femtosecond Alexandrite laser passively mode-locked by InP/InGaP quantum-dot saturable absorber

Shirin Ghanbari, Ksenia Fedorova, Andrey Krysa, Edik Rafailov, and Arkady Major

Doc ID: 313056 Received 08 Nov 2017; Accepted 07 Dec 2017; Posted 07 Dec 2017  View: PDF

Abstract: An Alexandrite laser passively mode-locked using an InP/InGaP quantum-dot semiconductor saturable absorber mirror (QD-SESAM) was demonstrated. The laser was pumped at 532 nm and generated 380 fs and 420 fs pulses at 775 nm with an average output power of 295 mW and 325 mW, respectively. To the best of our knowledge, this is the first report on a passively mode-locked femtosecond Alexandrite laser using a SESAM in general and a quantum-dot SESAM in particular.

Poincaré sphere representation for spatially varying birefringence

Anthony Vella and Miguel Alonso

Doc ID: 309758 Received 24 Oct 2017; Accepted 06 Dec 2017; Posted 11 Dec 2017  View: PDF

Abstract: The Poincaré sphere is a well-known graphical tool for representing the polarization of light in a three-dimensional space. Similarly, an optical element with spatially varying birefringence can be represented by a surface on a four-dimensional "Poincaré hypersphere". A projection of this surface onto the traditional Poincaré sphere provides an intuitive geometric description of the polarization transformation performed by the element. We apply this formalism to quantify the effects of birefringence on the image quality of an optical system.

Filamentation-free self-compression of mid-infrared pulses in birefringent crystals with second-order cascading-enhanced self-focusing nonlinearity

Rosvaldas Suminas, Gintaras Tamosauskas, and Audrius Dubietis

Doc ID: 312485 Received 02 Nov 2017; Accepted 05 Dec 2017; Posted 07 Dec 2017  View: PDF

Abstract: We experimentally demonstrate virtually lossless, filamentation-free and energy-scalable more than three-fold self-compression of mid-infrared laser pulses at 2.1 μm in a birefringent medium (β-BBO crystal), which stems from favorable interplay between the second-order cascading-enhanced self-phase modulation and anomalous group velocity dispersion. By choosing an appropriate input beam diameter and intensity, the self-compression down to sub-30 fs pulse widths with GW peak power is achieved without the onset of beam filamentation and associated nonlinear losses due to the multiphoton absorption, yielding the energy throughput greater than 86%.

Ultra-high speed RF filtering switch based on stimulated Brillouin scattering

Hengyun Jiang, Lianshan Yan, Wei Pan, Bing Luo, and Xihua Zou

Doc ID: 309430 Received 18 Oct 2017; Accepted 05 Dec 2017; Posted 11 Dec 2017  View: PDF

Abstract: RF filtering switch is highly desired for signal routing or manipulation in the RF system. Based on the stimulated Brillouin scattering effect and electro-optics Pockels effect, we proposed a novel RF filtering switch with a high frequency filtering precision and a fast switching speed. We have experimentally demonstrated the RF filtering with a high precision of ~34MHz, a wide operation bandwidth of ~18GHz and the RF switching at a speed of <100ps, which is hundreds of times faster than the traditional RF switch.

Single-shot Fourier ptychography based on diffractively beam splitting

Xiaoliang He, cheng liu, and Jianqiang Zhu

Doc ID: 310079 Received 26 Oct 2017; Accepted 05 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: An optical setup and corresponding reconstruction method are proposed to realize single shot Fourier ptychography(FP). Multiple angle-varied object waves are generated by placing a dammann grating at a certain distance behind the object, and the generated image array of low resolution corresponding to different diffraction orders formed on the detector plane is recorded simultaneously in a single exposure. The amplitude as well as the phase information of the object can be properly reconstructed with standard FP algorithm from the recorded image array. This method eliminates the requirement for the angular scanning of standard FP, and the total acquisition time is dramatically reduced. The feasibility of this proposed method was demonstrated both numerically and experimentally. The proposed method can drastically improve the performance of standard FP technique and make it very suitable for applications, where high imaging speed is required

Comparison of optical feedback dynamics of InAs/GaAs quantum dot lasers emitting solely on ground or excited states

Lyu-Chih Lin, Chih-Ying Chen, Heming Huang, Dejan Arsenijević, Dieter Bimberg, Frederic Grillot, and Fan-Yi Lin

Doc ID: 312950 Received 09 Nov 2017; Accepted 05 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: We experimentally compare the dynamics of InAs/GaAs quantum dot lasers under optical feedback emitting exclusively on ground (GS) or excited (ES) states. By varying the feedback parameters and put focus either on their short and long cavity regions, various periodic and chaotic oscillatory states are found. The GS laser is shown to be more resistant to feedback, benefiting from its strong relaxation oscillation damping. In contrast, the ES laser can easily be driven into complex dynamics. While the GS laser is of importance for the development of isolator-free transmitters, the ES laser is essential for applications taking advantages of chaos.

Relative sensitivity variation law in the field of fluorescence intensity ratio thermometry

Leipeng Li, Yuan Zhou, feng qin, Yangdong Zheng, Hua Zhao, and Zhiguo Zhang

Doc ID: 313060 Received 09 Nov 2017; Accepted 04 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: We study the variation law of relative sensitivity in the field of fluorescence intensity ratio thermometry. It is theoretically demonstrated that there must be only one maximum value of relative sensitivity upon the case where there is a positive offset in fitting function. Moreover, the method to obtain this maximum is proposed. Experimental results, taking the 5D1/5D0 levels of Eu3+ as examples, are in excellent accordance with the conclusion. The mechanism behind is then investigated, and other populating processes imposed on the 5D1 level which exert negative outcome on thermal sensitivity are found to play a key role in determination of this unique variation law.

Multi-electrode tunable liquid crystal lenses with one lithography step

Jeroen Beeckman, Tzu-Hsuan Yang, Inge Nys, John George, Tsung-Hsien Lin, and Kristiaan Neyts

Doc ID: 309665 Received 20 Oct 2017; Accepted 04 Dec 2017; Posted 05 Dec 2017  View: PDF

Abstract: Electrically tunable lenses offer the possibility to control the focal distance by applying an electric field. Different liquid crystal tunable lenses have been demonstrated. In order to minimize lens aberrations, multi-electrode designs allow to fine-tune the applied voltages for every possible focal distance. In this article we provide a novel multi-electrode design in which only one lithography step is necessary, thereby offering a greatly simplified fabrication procedure compared to earlier proposed designs. The key factor is the use of a high-permittivity layer in combination with floating electrodes.

Ultrafast saturable absorption of MoS2 nanosheets under different pulse-width excitation conditions

Juna Zhang, Hao Ouyang, Xin Zheng, Jie You, Runze Chen, Tong Zhou, Yizhen Sui, Yu Liu, Xiang'ai Cheng, and Tian Jiang

Doc ID: 314406 Received 28 Nov 2017; Accepted 04 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: The newly raised two-dimensional material MoS2 is regarded as an ideal candidate for saturated absorbers. Here, the open-aperture Z-scan method is used to study the saturation absorption (SA) response of monolayer and multilayer MoS2, considering laser irradiation with different pulse-width. Specifically, in cases of 10 ns and 10 ps laser pulses, the accumulative nonlinearity (e.g., free carrier absorption (FCA)) coupled with SA is found in both monolayer and multilayer MoS2. However, under a 65 fs pulse laser, the instantaneous nonlinearity (e.g., two photon absorption (TPA)) and the SA effect turn to play a significant role. Additionally, the saturation of both TPA and FCA is observed in MoS2. Importantly, the modulation depth of MoS2 shows different change trends by adjusting the laser pulse-width.

Equivalence principle and quantum mechanics: quantum simulation with entangled photons

Stefano Longhi

Doc ID: 312698 Received 03 Nov 2017; Accepted 04 Dec 2017; Posted 04 Dec 2017  View: PDF

Abstract: Einstein‘s equivalence principle states the complete physical equivalence of a gravitational field and corresponding inertial field in an accelerated reference frame. However, to what extent the equivalence principle remains valid in non-relativistic quantum mechanics is a controversial issue. To avoid violation of the equivalence principle, Bargmann‘s superselection rule forbids a coherent superposition of states with different masses. Here we suggest a quantum simulation of non-relativistic Schroedinger particle dynamics in non-inertial reference frames, which is based on propagation of polarization-entangled photon pairs in curved optical waveguides. Violation of the equivalence principle can be detected in a Hong-Ou-Mandel quantum interference measurement.

Quantum limits on the time-bandwidth product of an optical resonator

Mankei Tsang

Doc ID: 308617 Received 05 Oct 2017; Accepted 03 Dec 2017; Posted 04 Dec 2017  View: PDF

Abstract: A thought-provoking proposal by Tsakmakidis et al. [Science 356, 1260 (2017)] suggests that nonreciprocal optics can break a time-bandwidth limit to passive resonators. Here I quantize their resonator model and show that quantum mechanics does impose a limit, or else requires extra noise to be added in the same fashion as amplified spontaneous emission in active resonators. I also use thermodynamics to argue that extra dissipation or noise must be present in their proposed device.

Aberration-free calibration for 3D single molecule localization microscopy

Clément Cabriel, Nicolas Bourg, Guillaume Dupuis, and Sandrine Leveque-Fort

Doc ID: 309151 Received 13 Oct 2017; Accepted 03 Dec 2017; Posted 04 Dec 2017  View: PDF

Abstract: We propose a straightforward sample-based technique to calibrate the axial detection in 3D single molecule localization microscopy (SMLM). Using microspheres coated with fluorescent molecules, the calibration curves of PSF-shaping- or intensity-based measurements can be obtained for any required depth range from a few hundreds of nm to several tens of µm. This experimental method takes into account the effect of the spherical aberration without requiring computational correction.

Measurements of milli-Newton surface tension forces with tilted fiber Bragg gratings

Yu Shen, Chuan Zhong, Dejun Liu, Xiaokang Lian, Jianyao Zheng, Jing Jing Wang, Yuliya Semenova, Gerald Farrell, Jacques Albert, and John Donegan

Doc ID: 308747 Received 09 Oct 2017; Accepted 03 Dec 2017; Posted 07 Dec 2017  View: PDF

Abstract: Small lateral forces (lower than 0.1 N) cannot normally be measured with conventional single mode fiber-based sensors because of the high value of their Young modulus (>70 GPa). Here we demonstrate the measurement of lateral forces in the range from 0.2-1.4×10-3 N with a tilted fiber Bragg grating (TFBG) in conventional single-mode fiber pushed against the surface tension of a bead of water. The measured transmission changes of individual cladding mode resonances of the TFBG corresponding to these force values are of the order of 29 dB. Separate measurements of the contact angle between the surface of the water and the fiber are used to calibrate the sensor with help from the known value of surface tension for water. Once calibrated, a TFBG can be used to measure unknown forces in the same range or to measure an unknown surface tension, provided a separate force measurement is available.

2 µm Doppler wind lidar with a Tm:fiber laser-pumped Ho:YLF laser

Kohei Mizutani, Shoken Ishii, Makoto Aoki, Hironori Iwai, Ryohei Otsuka, Hirotake Fukuoka, Takayoshi Ishikawa, and Atsushi Sato

Doc ID: 314273 Received 29 Nov 2017; Accepted 02 Dec 2017; Posted 07 Dec 2017  View: PDF

Abstract: A 2 µm Ho:YLF laser end-pumped by a 1.94 µm Tm:fiber laser was developed. A laser system of ring resonator oscillator and amplifier was operated at repetition rates of 200–5000 Hz at room temperature. The Q-switched outputs were 7.4 W at 5000 Hz and 4.25 W at 200 Hz. Injection seeding was applied to the ring resonator and single-mode laser emission was obtained. The Tm:fiber laser pumped Ho:YLF laser was first used for Doppler wind lidar measurements, and wind profiles were obtained up to ranges of about 15 km in a range resolution of 96 m and an integration time of 1 second.

25 W single-frequency, low noise fiber MOPA at 1120 nm

benoit gouhier, Germain Guiraud, sergio rota-rodrigo, jian zhao, Nicholas Traynor, and GIORGIO SANTARELLI

Doc ID: 308724 Received 18 Oct 2017; Accepted 02 Dec 2017; Posted 13 Dec 2017  View: PDF

Abstract: This letter reports on the development of a 25 W single-frequency, all-fiber master-oscillator power amplifier operating at 1120 nm. By heating the gain fiber at 75 ˚C, an output power of 25.3 W is achieved with an optical-to-optical efficiency of 53.5 %. The output shows no sign of stimulated Brillouin scattering and the signal to amplified spontaneous emission ratio is close to 40 dB. A M2 value of 1.15 and a polarization extinction ratio of 17 dB are measured. The relative intensity noise of the output is also characterized, reaching -155 dBc/Hz at 10MHz at the maximum output power. The study of the noise dynamics highlights for the first time to the best of our knowledge an unpredicted behavior due to the strong amplified spontaneous emission.

Evanescent field refractometry in planar optical fiber

Christopher Holmes, Alex Jantzen, Alan Gray, Paul Gow, Lewis Carpenter, Rex Bannerman, James Gates, and Peter Smith

Doc ID: 309889 Received 25 Oct 2017; Accepted 01 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: This work demonstrates a refractometer in Integrated OpticalFiber (IOF), a new optical platform that planarizes fiber usingflame hydrolysis deposition (FHD). The unique advantage of thetechnology is its survivability in harsh environments. Theplatform is mechanically robust, can survive elevatedtemperatures approaching 1000oC and exposure to commonsolvents, including acetone, petrol and methanol. For thedemonstrated refractometer, fabrication was achieved throughwet etching an SMF-28 fiber to a diameter of 8 μm before FHDplanarization. External refractive index was monitored usingfiber Bragg gratings, written into the core of the planarizedfiber. A direct comparison to alternative fiber Bragg gratingrefractometers is made. The developed platform is shown tohave comparable sensitivities, with the added advantage ofsurvivability in harsh environments.

Real-time Fourier transformation based on bandwidth magnification of RF signal

Yan Zheng, Jilong Li, Yitang Dai, Feifei Yin, and Kun Xu

Doc ID: 312648 Received 03 Nov 2017; Accepted 01 Dec 2017; Posted 04 Dec 2017  View: PDF

Abstract: We demonstrate a novel real-time Fourier transformation (RTFT) scheme with MHz-level resolution realized by bandwidth magnification of radio frequency (RF) signal. Before the frequency-to-time mapping, the RF signal is modulated on an optical frequency comb, and then extracted by a Vernier comb filter. As a result, RF components can be separated in spectrum with greatly magnified optical bandwidth. So, even with limited dispersion provided by ordinary optical fiber, the frequency-dependent pulses can be distinguished in time domain. Experimentally, the RF signal where the frequency difference is 60 MHz is separated by around 1 -ps in time domain, equivalent to the dispersion of 1975.5 ps/GHz (247000 ps/nm), while the physical dispersion is 1500 ps/nm. Thus, based on the bandwidth magnification of RF signal, the dispersion is equivalently amplified by 165 times.

Scattering cross section modulation in photoacoustic remote sensing microscopy

Kevan Bell, Parsin Haji Reza, and Roger Zemp

Doc ID: 307975 Received 27 Sep 2017; Accepted 01 Dec 2017; Posted 01 Dec 2017  View: PDF

Abstract: Modeling and observations of large scattering cross-section modulations in absorbing optical scatterers due to a pulsed laser excitation is reported. Rapid laser-induced thermo-elastic expansion produces non-trivial perturbations to the local refractive indicies. This mechanism forms the basis of a recent non-contact photoacoustic technique known as photoacoustic remote sensing (PARS) microscopy. A time-evolution model is constructed and discussed, comparing with existing planar models, time-independent models, and experiments. Fractional scattering cross-section modulations greater than 20 times that of the unperturbed particles are predicted and observed for the first time. A non-linear acoustic enlargement effect is likewise predicted and observed. Implications of system and material properties are explored.

A differential loss, magnetic field sensor using a ferrofluid encapsulated D-shaped optical fiber

Georgios Violakis, Nikolaos Korakas, and Stavros Pissadakis

Doc ID: 308142 Received 02 Oct 2017; Accepted 01 Dec 2017; Posted 01 Dec 2017  View: PDF

Abstract: A ferrofluid encapsulated, D-shape optical fiber exhibits differential loss with respect to magnetic field placed azimuthally around its longitudinal axis, manifested in its transmission power measured. Experimental results obtained show that differential loss changes up to 12dB are measured versus magnetic field azimuthally placed with respect to the longitudinal axis of the D-shape optical fiber. Investigating the underlying physical mechanisms involved, magneto-induced refractive index and loss measurements using ferrofluid overlaid diffractive elements, reveal a differential loss mechanism associated with the relative light polarization direction and the magnetic field application direction; also used for performing modal profile simulations of ferrofluid immersed D-shape optical fiber. It is demonstrated that such an optical system can act as a magnetic field sensor with field angle and intensity sensing capabilities.

Photoacoustic and hyperspectral dual-modality endoscope

liu ning, Sihua Yang, and Da Xing

Doc ID: 308566 Received 05 Oct 2017; Accepted 01 Dec 2017; Posted 01 Dec 2017  View: PDF

Abstract: We have developed a dual-modality endoscope composed of photoacoustic (PA) and Hyperspectral imaging (HSI), capable of visualizing both structural and functional properties of bio-tissue. The endoscope’s composition and scanning mechanism was described, and the feasibility and ability of the dual-modality endoscope was verified by mimic phantom experiments. Late we demonstrated its endoscopic workability through in-vivo experiments. The experimental results showed that the proposed herein hybrid endoscope can provide optical imaging of the surface and tomography imaging for the deeper features, and oxygen saturation map of the same imaging area. We demonstrated optical-resolution photoacoustic imaging of microvascular structures and oxygen saturation map in a rabbit’s rectum. It confirmed that this dual-modality endoscope can play an important role in comprehensive clinical applications.

Observation of Spatial Optical Diametric Drive Acceleration in Photonic Lattices

Yumiao Pei, Yi Hu, Cibo Lou, Daohong song, Liqin Tang, Jingjun Xu, and Zhigang Chen

Doc ID: 312739 Received 06 Nov 2017; Accepted 01 Dec 2017; Posted 01 Dec 2017  View: PDF

Abstract: We experimentally and theoretically demonstrate a spatial diametric drive acceleration of two mutually incoherent optical beams in one dimensional optical lattices under a self-defocusing nonlinearity. The two beams, exciting the modes at the top/bottom edges of the first Bloch band and hence experiencing normal/ anomalous diffraction, can bound together and bend in the same direction during nonlinear propagation, analogous to the interplay between two objects with opposite signs of mass that breaks the Newton’s third law. Their spatial spectrum changes associated with the acceleration are analyzed for different lattice modulations. We find that the acceleration limit is determined by the beam exciting the top bandedge that reaches a saturated momentum change prior to the other pairing beam.

Iodine-Stabilized Single-Frequnecy Green InGaN Diode Laser

Yi-hsi Chen, Lin Chen, Jow-Tsong Shy, and Hsiang-Chen Chui

Doc ID: 306892 Received 09 Oct 2017; Accepted 30 Nov 2017; Posted 01 Dec 2017  View: PDF

Abstract: A 520-nm InGaN diode laser can emit a mW-level, single-frequency laser beam when the applied current (1.04Ith) slightly exceeds the lasing threshold. Laser frequency was stabilized onto hyperfine transitions of iodine molecules through saturated–absorption spectroscopy. The uncertainty of frequency stabilization was approximately 8x10−9 at a 10-s integration time. The stabilized laser frequency was insensitive to diode temperature and could be finely tuned by adjusting the applied current. A single longitudinal mode operational region with diode temperature, current, and output power was investigated. The proposed compact scheme can replace conventional green-diode-pumped solid-state lasers and applied as frequency standards.

Cascaded four-wave-mixing in the extreme ultraviolet region

Lap Dao, Khoa Anh Tran, and Peter Hannaford

Doc ID: 309508 Received 23 Oct 2017; Accepted 30 Nov 2017; Posted 01 Dec 2017  View: PDF

Abstract: We present a detailed study of the wave-mixing process in the extreme ultraviolet region (around 30 nm) by using two collinear multiple-cycle laser pulses with incommensurate frequencies (wavelengths 1400 nm and 800 nm). The experimental data provides evidence for the coherent accumulation of wave-mixing fields and a high third-order response of the medium in this spectral range. We show that the time evolution of the mixing fields can be used to study the coherence dynamics of the free electron wave-packet with a lifetime of 200 – 750 fs.

Efficient, 2-5 μm tunable CdSiP2 optical parametric oscillator pumped by a laser source at 1.57 μm

L. A. Pomeranz, John McCarthy, randy day, Kevin Zawilski, and Peter Schunemann

Doc ID: 308571 Received 04 Oct 2017; Accepted 29 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: We report on first demonstrations of CdSiP2 (CSP) based optical parametric oscillators that are pumped by eye safe Q-switched nanosecond laser sources operating at 1.57 μm. One device reached 40% optical conversion efficiency generating 10 mJ of energy near degeneracy in the 3 micron region. Angle tuning of a similar device through the middle infrared was demonstrated with the signal and idler waves being tuned from 2.28 to 5.05 μm.

Near quantum-noise limited and absolute frequency stabilized 1083 nm single-frequency fiber laser

Qilai Zhao, Kaijun Zhou, Zisheng Wu, Changsheng Yang, Zhouming Feng, Huihui Cheng, Jiulin Gan, Mingying Peng, Zhongmin Yang, and Shanhui Xu

Doc ID: 307847 Received 25 Sep 2017; Accepted 29 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: The Earth’s magnetic field has significant effects, which can protect us from the cosmic radiation and provide navigation for biological migration. However, slow temporal variations originating in the liquid outer core invariably exist. To understand the working mechanism of the geomagnetic field and improve the accuracy of navigation systems, a high-precision magnetometer is essential to measure the absolute magnetic field. Helium optically pumping magnetometer is an advanced approach, but its sensitivity and accuracy are directly limited by the low-frequency relative intensity noise and frequency stability characteristics of light source. Here, we demonstrate a near quantum-noise limited and absolute frequency stabilized 1083 nm single-frequency fiber laser. The relative intensity noise is only 5 dB higher than the quantum-noise limit and the root-mean-square of frequency fluctuation is ~17 kHz after locked. This fiber laser could suppress the fluctuation of magnetic resonant frequency and improve the signal-to-noise ratio of the magnetic resonance signal detection.

High-throughput microchannels fabrication in fused silica by temporally shaped femtosecond laser Bessel beam assisted chemical etching

Zhi Wang, Lan Jiang, Xiaowei Li, Andong Wang, Zhulin Yao, Kaihu Zhang, and Yongfeng Lu

Doc ID: 307957 Received 26 Sep 2017; Accepted 29 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: We proposed to combine temporally shaped (double-pulse train) laser pulses with spatially shaped (Bessel beam) laser pulses. By using a temporally shaped femtosecond laser Bessel beam assisted chemical etching method, the energy deposition efficiency was improved by adjusting the pulse delay to yield a stronger material modification, and thus a higher etching depth. The etching depth was enhanced by a factor of 13 using the temporally shaped Bessel beam. The mechanism of etching depth enhancement was elucidated by localized transient free electrons dynamics-induced structural and morphological changes. Micro-Raman spectroscopy was conducted to verify the structural changes inside the material. This method enables high-throughput, high-aspect-ratio microchannels fabrication in fused silica for potential applications in microfluidics.

Spatiotemporal sharply autofocused dual-Airy-ring-Airy-Gaussian-vortex wavepackets

Jingli Zhuang, Xingyu Chen, Fang Zhao, Xi Peng, Dongdong Li, Liping Zhang, and Dongmei Deng

Doc ID: 309452 Received 19 Oct 2017; Accepted 29 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Here we investigate the propagation properties of spatiotemporal sharply autofocused single-Airy-ring-Airy-Gaussian-vortex(AiRAiGV) and dual-Airy-ring-Airy-Gaussian-vortex(dAiRAiGV) wavepackets by solving (3+1) D Schr\"{o}dinger equation in free space. We can change the spatial part of the wavepackets into Airy or Gaussian distribution by choosing the different spatial distribution factors $b_s$. In particular, only when the shape of pulses is set well with appropriate temporal distribution factor $b_t$ and initial velocity $v$ in temporal domain, dAiRAiGV wavepackets can simultaneously autofocus in spatial and temporal domain and the peak intensity has been increased dozens of times at the focus more than that at the initial plane. Furthermore, properties of dAiRAiGV wavepackets with a vortex in the center and off-axis vortex pairs are also discussed.

Subwavelength wave manipulation in a thin surface-wave band-gap crystal

Zhen Gao, Wang Zhuoyuan, and Baile Zhang

Doc ID: 310067 Received 26 Oct 2017; Accepted 29 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: It has been recently reported that the unit cell of wire media metamaterials can be tailored locally to shape the flow of electromagnetic waves at deep subwavelength scales [Fabrice et al., Nature Physics 9, 55-60 (2013)]. However, such bulk structures have a thickness of at least the order of wavelength, thus hindering their applications in the on-chip compact plasmonic integrated circuits. Here, based upon a Sievenpiper “mushroom” array [Sievenpiper et al., IEEE Trans. Microwave Theory Tech. 47, 2059 (1999)] which is compatible with the standard printed circuit board technology, we propose and experimentally demonstrate the deep-subwavelength manipulation of surface waves on a thin surface-wave band-gap crystal with a thickness much smaller than the wavelength (1/40th of the operating wavelength). Functional devices including T-shaped splitter and sharp bend are constructed with good performance.

Nonlinear absorption and temperature-dependent fluorescence of perovskite FAPbBr3 nanocrystal

Lan Yang, Ke We, Zhongjie Xu, Feiming Li, Runze Chen, Xin Zheng, Xiang'ai Cheng, and Tian Jiang

Doc ID: 314004 Received 21 Nov 2017; Accepted 28 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Recent progress in solar cell and light emitting devices makes halide perovskite a research hot-spot in optics. In this paper, the nonlinear absorption and fluorescence properties of FAPbBr3 nanocrystal, one typical organometallic halide perovskite, have been investigated via Z-scan measurements and density-dependent photoluminescence (PL) spectrum. The FAPbBr3 nanocrystal exhibits nonlinear absorption under the excitation of 800 nm, whose photon energy is below the bandgap of FAPbBr3. The significant absorption is experimentally confirmed to be induced by two photon absorption (TPA) and the TPA coefficient is measured to be ~0.0042 cm∕GW. Moreover, the PL induced by TPA in FAPbBr3 nanocrystal shows different temperature-dependent behaviours in the range from 90 K to 350 K. The peaks of PL spectrum remain nearly constant at 100 K ~ 160 K, with a very shallow trough at around 150 K, while a linear blue-shift (0.496 meV/K) of the spectrum is observed when temperature is above 160 K. These temperature-dependent fluorescence behaviors can be ascribed to the structural phase transition at about 150 K and the contribution of thermal expansion. Moreover, the exciton binding energy of 62.4 meV and the optical phonon energy of 15.3meV are also extracted from the temperature-dependent PL data.

13dB Squeezed Vacuum States at 1550nm from 12mWexternal pump power at 775nm

Axel Schoenbeck, Fabian Thies, and Roman Schnabel

Doc ID: 309165 Received 16 Oct 2017; Accepted 28 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: Strongly squeezed light at telecommunication wavelengths is the necessary resource for one-sided device-independent quantum key distribution via fibre networks. Reducing the optical pump power that is required for its generation will advance this quantum technology towards efficient out-of-laboratory operation. Here, we investigate the second-harmonic pump power requirement for parametric generation of continuous-wave squeezed vacuum states at 1550nm in a state-of-the-art doubly-resonant standing-wavecavity setup. We use coarse adjustment of the cavity length together with temperature fine-tuning for simultaneously achieving double resonance and quasi phase matching, and observe a squeeze factor of 13dB at 1550nm from just 12mW external pump power at 775nm. We anticipate that optimizing the cavity coupler reflectivity will reduce the external pump power to 3mW, without reducing the squeeze factor.

Polarization-insensitive and wide-incident-angle optical absorber with periodically patterned graphene-dielectric arrays

Xiujuan Zou, Gaige Zheng, Jiawei Cong, Linhua Xu, Yunyun Chen, and Min Lai

Doc ID: 309521 Received 18 Oct 2017; Accepted 28 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: A polarization-insensitive and angle-independent graphene absorber (GA) with periodically patterned grating is demonstrated. A periodic nanocavity composed of multilayer subwavelength grating and metal substrate supports a strongly localized mode inside the cavity, where the mode helps to absorb more electromagnetic (EM) waves. The proposed GA exhibits polarization-insensitive behavior and maintains the high absorption above 90% up to a wide range of incident angle (more than 80°). We attribute the high absorption to the excitation of the cavity mode resonance (CMR) and magnetic resonance (MR) for the TE and TM polarizations, respectively. The proposed graphene absorber has potential applications in the design of various devices such as optical modulators or tunable absorption filters because of its remarkable angle-insensitive absorption performance.

Broadband near-infrared antireflection coatings fabricated by three dimensional direct laser writing

Yanzeng Li, Daniel Fullager, Edison Angelbello, Darrell Childers, Glenn Boreman, and Tino Hofmann

Doc ID: 308273 Received 03 Oct 2017; Accepted 28 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: Three-dimensional direct laser writing via two photon polymerization is used to fabricate anti-reflective structured surfaces composed of sub-wavelength conicoid features optimized to operate over a wide bandwidth in the near-infrared range from 3700 cm-1 to 6600 cm-1 (2.7 to 1.52 μm). Analytic Bruggemann effective medium calculations are used to predict nominal geometric parameters such as the fill factor of the constitutive conicoid features of the anti-reflective structured surfaces presented here. The performance of the anti-reflective structured surfaces was investigated experimentally using infrared transmission measurements. An enhancement of the transmittance by 1.35% to 2.14% over a broadband spectral range from 3700 cm-1 to 6600 cm-1 (2.7 to 1.52 μm) was achieved. We further report on finite-element-based reflection and transmission data using three-dimensional model geometries for comparison. A good agreement between experimental results and the finite-element-based numerical analysis is observed once as-fabricated deviations from the nominal conicoid forms are included in the model. Three-dimensional direct laser writing is demonstrated here as an efficient method for the fabrication and optimization of anti-reflective structured surfaces designed for the infrared spectral range.

Non-diffracting beams for label-free imaging through turbid media

Harel Nagar, Elad Dekel, Dror Kasimov, and Yael Roichman

Doc ID: 312499 Received 07 Nov 2017; Accepted 28 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: We propose a new method to image through dynamically changing turbid media based on scanning of non-diffractive laser beams. We use computer generated holograms to create Airy beams and compare quantitatively the characteristics of their propagation in clear and turbid media. Imaging contrast is achieved by relative reflection of the scanned beams from the imaged surface. We implement our method to demonstrate experimentally our ability to image a chromium surface on a glass slide through 270 um of highly scattering milk/water mixtures with a resolution of several microns.

TE-polarized design for metallic slit lenses: a way to deep-subwavelength focusing over a broad wavelength range

Yechuan Zhu, Weizheng Yuan, Wenli Li, Hao Sun, Kunlun Qi, and Yiting Yu

Doc ID: 313047 Received 08 Nov 2017; Accepted 27 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: Slit arrays based on noble metals have been widely proposed as planar transverse-magnetic-(TM)-lenses, illuminated by a linearly polarized light with the polarization perpendicular to slits and implementing the focusing capability beyond the diffraction limit. However, due to intrinsic plasmonic losses, these TM-lenses cannot work efficiently in the ultraviolet wavelengths. In this letter, taking advantage of the unique transmission through metallic slits not involving plasmonic losses, a metallic slit array with transverse-electric (TE) polarized design is proposed, showing for the first time, to the best of our knowledge, the realization of sub-diffraction-limit focusing for ultraviolet light. Additionally, in contrast to the situations of TM-lenses, a wider slit leads to a greater phase delay and much larger slits can be arranged to construct the TE-lenses, which is quite beneficial for practical nanofabrication. Furthermore, deep-subwavelength focusing can be achieved by utilizing the immersing technology.

Plasmon mediated inverse Faraday effect in graphene - dielectric - metal structure

Igor Bychkov, Dmitry Kuzmin, Valentine Tolkachev, Pavel Plaksin, and Vladimir Shavrov

Doc ID: 311254 Received 31 Oct 2017; Accepted 27 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: The present Letter shows the features of inverse Faraday effect in the graphene-dielectric-metal (GDM) structure. The constants of propagation and attenuation of the surface plasmon-polariton modes are calculated. The effective magnetic field induced by surface plasmon modes in the dielectric due to the inverse Faraday effect is estimated to reach above 1 tesla. The possibility to control the distribution of the magnetic field by chemical potential of graphene is shown. The concept of strain-driven control of the inverse Faraday effect in the structure has been proposed and as well investigated.

Fabrication of helical photonic structures with submicrometer axial and spatial periodicities following ‘inverted umbrella’ geometry through phase controlled interference lithography

Saraswati Behera, Swagato Sarkar, and Joby Joseph

Doc ID: 306516 Received 05 Sep 2017; Accepted 27 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: In this paper, we report for the first time a phase SLM based interference lithography approach for the realization of hexagonally packed helical photonic structures with submicrometer scale spatial as well as axial periodicity over large area. A phase only spatial light modulator is used to electronically generate six phase controlled plane beams. These six beams from the front side and a direct central backside beam are used together in an “inverted umbrella” geometry setup to realize the desired submicrometer axial periodic chiral photonic structures through interference lithography. The realized structures with 650 nm spatial and 353 nm axial periodicities on negative photoresist can be used as an optical filter and refractive index sensor as evidenced from the FDTD based simulation study on its optical properties. Further, the fabricated templates can be transferred to metals such as silver or aluminum for the realization of metamaterial based broadband circular polarizer ranging from 1-3.5 µm NIR spectra.

Polarization control of terahertz radiation from two-color femtosecond gas breakdown plasma

Olga Kosareva, Mikhail Esaulkov, Nikolay Panov, Vera Andreeva, Daniil Shipilo, Petr Solyankin, Ayhan Demircan, Ihar Babushkin, Vladimir Makarov, Uwe Morgner, Alexander Shkurinov, and Andrei Save'ev

Doc ID: 307555 Received 22 Sep 2017; Accepted 26 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We individually control polarizations of the 800-nm and 400-nm beams, which form the two-color femtosecond plasma filament in air irradiating linear-to-elliptical THz signal. We detected the threshold-like appearance of THz ellipticity at the angle of ~85º between the fundamental and the second harmonic field polarization directions. The simulations confirm the abrupt change of THz polarization and reveal that the weak ellipticity of the second harmonic is sufficient to generate essentially elliptical THz radiation.

Quadrature squeezing of a higher-order sideband spectrum in cavity optomechanics

Shaopeng Liu, Wen-Xing Yang, Zhonghu Zhu, Tao Shui, and Ling Li

Doc ID: 309605 Received 19 Oct 2017; Accepted 26 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We propose an efficient scheme to generate quadrature squeezing of higher-order sideband spectrum in an optomechanical system. That is achieved by exploiting a well-established optomechanical circumstance,where a second-order nonlinearity is embedded into the optomechanical cavity driven by a strong control field and a weak probe pulse. Using experimentally achievable parameters, we demonstrate that thesecond-order nonlinearity intensity and the frequency detuning of control field allow us to modify the amplitude of higher-order sidebands and improve the amount of squeezing of higher-order sideband spectrum. Furthermore, in the presence of a strong second-order nonlinearity, an optimizing quadrature squeezing of higher-order sideband spectrum can be achieved, which provides a practical opportunity to design the squeezed frequency combs and others precision measurement.

Absorption of laser plasma in competition with oscillation currents for terahertz spectrum

Xiaolu Li, Ya Bai, Na Li, and Peng Liu

Doc ID: 309865 Received 24 Oct 2017; Accepted 26 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: We generate terahertz radiation in a supersonic jet of nitrogen molecules pumped by intense two-color laser pulses. The tuning of terahertz spectra from blue-shift to red-shift is observed by increasing laser power and stagnation pressure, and the red-shift range is enlarged with the increased stagnation pressure. Our simulation reveals that the plasma absorption of the oscillation currents and expanded plasma column owing to increased laser intensity and gas number density are crucial factors in recurrence of the red-shift of terahertz spectra. The findings disclose the microscopic mechanism of terahertz radiation and present a controlling knob for the manipulation of broadband terahertz spectrum from laser plasma.

Doppler-free Fourier transform spectroscopy

Samuel Meek, Arthur Hipke, Guy Guelachvili, Theodor Haensch, and Nathalie Picque

Doc ID: 308719 Received 20 Oct 2017; Accepted 25 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: Sub-Doppler broadband multi-heterodyne spectroscopy is proposed and experimentally demonstrated. Using two laser frequency combs of slightly different repetition frequencies, we have recorded Doppler-free two-photon dual-comb spectra of atomic rubidium resonances of a width of 6 MHz, while simultaneously interrogating a spectral span of 10 THz. The atomic transitions are uniquely identified via the intensity modulation of the observed fluorescence radiation. These results, which -to our knowledge- represent the first demonstration of Doppler-free Fourier transform spectroscopy, extend the range of applications of broadband spectroscopy towards precision nonlinear spectroscopy.

Silicon-on-insulator microring resonator sensor based on amplitude comparison sensing function

Wenjian Yang, SHIJIE SONG, Xiaoke Yi, Suen Xin Chew, Liwei Li, and Linh Nguyen

Doc ID: 308638 Received 05 Oct 2017; Accepted 25 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: A novel highly sensitive integrated sensor based on silicon-on-insulator microring resonator is proposed and experimentally demonstrated. To achieve a fast-response and cost-effective sensing system, the new structure establishes an amplitude comparison sensing function (ACSF), which monitors the optical power from both through port and drop port of an add-drop microring resonator simultaneously. A highly enhanced linear relationship between the resonant wavelength shift and the ACSF value is achieved with R-squared value over 0.99. Meanwhile, the structure can also eliminate the unexpected power fluctuation of the input laser. Experiment demonstrates an almost constant ACSF with only ±0.9% discrepancy while the laser power is varied between 0 dBm to -7 dBm.

Dispersion-managed Ho-doped fiber laser mode-lockedwith graphene saturable absorber

Maria Pawliszewska, Tadeusz Martynkien, aleksandra przewłoka, and Jaroslaw Sotor

Doc ID: 309690 Received 20 Oct 2017; Accepted 25 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: In this work we demonstrate an all-fiber holmium-doped laser operating in the stretched-pulse regime. As a result of dispersion management, the laser is capable of generating 190 fs pulses with bandwidth of 53.6 nm. The pulses centered at 2060 nm reach 2.55 nJ of energy. Mode-locking is achieved with multilayer graphene saturable absorber. The paper also presents measurement of group velocity dispersion of active (Nufern SM-HDF-10/130), passive (SMF28), and dispersion compensating (Nufern UHNA4) fibers in 1.8 - 2.1 μm range. This is the first report on an all-fiber, stretched-pulse laser operating beyond 2 μm with nanomaterial-based saturable absorber.

Anisotropy of Nonlinear Optical Absorption of LBO Crystals at 355 nm

Oleg Vershinin, Aleksey Konyashkin, and Oleg Ryabushkin

Doc ID: 310110 Received 27 Oct 2017; Accepted 24 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: Dependence of nonlinear-optical absorption coefficient on intensity and polarization of pulsed laser radiation at 355 nm was investigated for LBO crystal using piezoelectric resonance laser calorimetry

Stable vortex soliton in nonlocal media with orientational nonlinearity

Yana Izdebskaya, Vladlen Shvedov, pawel jung, and Wieslaw Krolikowski

Doc ID: 308874 Received 11 Oct 2017; Accepted 23 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We report on the first experimental observation of stable vortex solitons in nematic liquid crystals with nonlocal nonlinear reorientational response. We show how these nonlinear vortex beams can be formed and confined in extraordinary optical waves by employing the cell with no lateral boundary conditions and the application of an external magnetic field that effectively controls the molecular direction and propagation of the self-trapped beams. We also find that these vortex solitons can be generated in certain ranges of the input beam power.

Orbital Angular Momentum Generation via Spiral Phase Microsphere

Yan Zhou, Gao Hui, Jinghua Teng, Xiangang Luo, and Minghui Hong

Doc ID: 309301 Received 17 Oct 2017; Accepted 23 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: Vortex beam carrying orbital angular momentum (OAM) attracts much attention in many research fields for its special phase and intensity distributions. In this letter, a novel design called the spiral phase microsphere (SPMS) is proposed for the first time which can convert incident plane wave light into the focused vortex beam that carries OAM with different topological charges l = ±1 and ±2. The vortex beam generation is verified by a self-interfered modification of the SPMS. Generation of the vortex beams by the SPMS irradiated by a single-wavelength incident light is studied using the CST MICROWAVE STUDIO simulation. SPMS provides a new approach to achieve high-efficiency and high-integrated photonic applications related with OAM.

Selective generation of Lamb modes by moving CW laser

Zheng Li, Alexey Lomonosov, Chenyin Ni, Bing Han, and Shen Zhong-Hua

Doc ID: 308314 Received 02 Oct 2017; Accepted 23 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: This paper focused on the selectively non-contact generation of Lamb wave modes in plates by using a continuous wave (CW) laser moving along sample surface. Compared with the generated Lamb waves with broadband, multiple modes (the existence of at least two modes at any given frequency) excited by pulsed laser, the desired single narrowband mode of Lamb wave can be generated by a moving CW laser, as long as the scanning speed matches with the phase velocity of the mode. Moreover, the dispersion curves of Lamb wave can be obtained directly from the power spectrum of the time-domain signal recorded at each laser moving speed. Single A0 mode excitation, coupled resonance phenomenon of A0 mode and S0 mode, single S0 mode excitation and high order modes appeared successively as scanning speed increases. Especially, the excitation of the pure single S0 mode can be realized which is suitable for propagation in the case of liquid loading. It is first proposed to realize the selection of a single Lamb wave mode by using the CW laser scanning method, which provides a brand-new way for the laser ultrasonic excitation.

Massive ordering and alignment of cylindrical micro-objects by photovoltaic optoelectronic tweezers

Iris Elvira, Juan Muñoz-Martínez, Álvaro Barroso, Cornelia Denz, José Bruno Ramiro, Angel Garcia-Cabañes, Fernando Agullo-Lopez, and Mercedes Carrascosa

Doc ID: 309968 Received 25 Oct 2017; Accepted 23 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: Optical tools for manipulation and trapping of micro- and nano-objects is a fundamental issue for many applications in nano and biotechnology. This work reports on the use of one of such methods, known as photovoltaic optoelectronics tweezers to orientate and organize cylindrical micro-crystals, specifically elongated zeolite L, on the surface of Fe-doped LiNbO3 crystal plates. Patterns of aligned zeolites have been achieved through the forces and torques generated by the bulk photovoltaic effect. The alignment patterns with zeolites parallel or perpendicular to the substrate surface are highly dependent on the features of the light distribution and the crystal configuration. Moreover, dielectrophoretic chains of zeolites with lengths up to 100 µm have been often observed. The experimental results of zeolite trapping and alignment have been discussed and compared together with theoretical simulations of the evanescent photovoltaic electric field and the dielectrophoretic potential. They demonstrate the remarkable capabilities of the optoelectronic photovoltaic method to orientate and pattern anisotropic microcrystals. The combined action of patterning and alignment offers an unique tool to prepare functional nanostructures with potential applications in a variety of fields such as non-linear optics, or plasmonics.

Geometrical optimization of nanostripes for surfaceplasmon excitation: an analytical approach

Thomas Grosges and Dominique Barchiesi

Doc ID: 309893 Received 24 Oct 2017; Accepted 23 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We give a simple tool for the optimization of the dimensions of a metallicnanostrip illuminated at a given wavelength under normal incidence,to get a maximum of the electromagnetic field amplitude in the nanostrip.We propose an analytical formula that gives the widths and the heights of the series of nanostripes that produce field enhancement.The validity of the analytical formula is checked by using Finite Element Method. This design of nanostrip could be useful for sensors and thermally active components.

Fabrication of optical vortices lattices based on holographic polymer dispersed liquid crystal films

Andy Y.-G. Fuh, YI LIN TSAI, Ching Han Yan, and Shing Trong Wu

Doc ID: 310072 Received 26 Oct 2017; Accepted 23 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: This study demonstrates optical vortices lattices based on holographic polymer stabilized liquid crystal films. The fabrication uses a phase only reflective spatial light modulator with numerically calculated phase profiles loaded on it to simplify the multi-helical-wave interference. The beam profiles of the diffraction beams are simulated using Fourier transformation and compared with the experimental results. The topological charges of the 1st order diffraction beams reconstructed from the HPDLC films are examined using Michelson interferometer.

High efficiency 2 μm Tm:YAP laser with a compact mechanical Q-switch

Brian Cole, Lew Goldberg, and Alan Hays

Doc ID: 309502 Received 18 Oct 2017; Accepted 22 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: We describe a compact, highly efficient, diode-pumped, mechanically Q-switched Tm:YAP laser operating near 2 μm. The Q-switch, based on a torsion spring resonant mirror scanner, had negligible optical loss and requiredvery low electrical drive power. At a 10 kHz pulse repetition frequency, the laser generated an average output power of 10.5 W at 1.94μm, Q-switched pulse energy of 1.05 mJ, pulse length of 31 ns, and a peak power of 34kW. The Q-switched laser exhibited maximum optical and electrical efficiencies of 51% and 26%, respectively

Flexible pulse-stretching for swept source at 2.0 µm using free-space angular-chirp-enhanced delay

Sisi Tan, Xiaoming Wei, Jianglai Wu, lingxiao yang, Kevin Tsia, and Kenneth Kin-Yip Wong

Doc ID: 309098 Received 16 Oct 2017; Accepted 22 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Dispersive pulse-stretching at 2.0 µm has long been hindered by the high intrinsic optical loss from conventional dispersive media. Here, a flexible pulse-stretching technique at 2.0 µm is demonstrated over a broad bandwidth with large-scale dispersion and low intrinsic optical loss. It employs the newly proposed pulse-stretching scheme, namely, free-space angular-chirp-enhanced delay (FACED). Both normal and anomalous temporal dispersion (up to ±500 ps/nm) with low intrinsic loss (< 6 dB) over a spectral bandwidth of ~84 nm at 2.0 µm is obtained with low nonlinear effects. Based on this method, optical wavelength-swept source at 2.0 µm is realized and applied to spectrally-encoded imaging at a line-scan rate of ~19 MHz, proving the potential of this pulse-stretching technique for continuous single-shot measurements at the 2.0-µm wavelength regime, particularly for optical microscopy and spectroscopy.

Fiber Bragg grating fabricated in micro-single-crystal sapphire fiber

Shuo Yang, Daniel Homa, Gary Pickrell, and Anbo Wang

Doc ID: 309905 Received 24 Oct 2017; Accepted 22 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: This Letter introduces a fiber Bragg grating in a micro-single-crystal sapphire fiber (micro-SFBG) for sensing applications in high temperature and harsh environments. The FBG was fabricated by a point-by-point method via an IR-femtosecond laser in a large diameter sapphire fiber that was then wet-hot acid etched to achieve microfiber size, which culminated in fabricating and characterizing a 9.6 μm-diameter micro-SFBG. The refractive index measurement ranging from 1 to 1.75 and temperature measurement from room temperature to 1400℃ are also reported.

Super pulses of orbital angular momentum in fractional-order spiroid vortex-beams

Alexander Volyar and Egorov Yuriy

Doc ID: 308262 Received 02 Oct 2017; Accepted 22 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We consider optical properties of Hypergeometric-Gaussian beam compositions with spiral-like intensity and phase distributions that are called the spiroid beams. Their orbital angular momentum as a function of a fractional-order topological charge has a chain of super-pulses (bursts and dips).The form of the super-pulses can be controlled by the spiral parameters. Such a phenomenon can be used in optical switches and triggers for optical devices and communication systems.

Wide-angle transmissions of electromagnetic fields through the sandwiched transparent epsilon-near-zero metamaterial screen

Rui Yang, Pei Yang, Yongchao Chen, Jiacheng Li, and Zhenya Lei

Doc ID: 308668 Received 09 Oct 2017; Accepted 22 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: We propose a sandwiched transparent epsilon-near-zero (ENZ) metamaterial screen to release the obliquely incident electromagnetic fields. More specifically, the transmission properties through ENZ metamaterials are investigated when incorporated with an interlayer of a meta-surface having periodic complementary spiral-resonator-matrixes. We show that both TE- and TM-polarized electromagnetic waves are capable of penetrating the ENZ metamaterials under a wide-angle range of illuminations, and the greatly enhanced transmissions are turning out to be frequency dispersionless for different polarized electromagnetic fields with different incident angles. Our design, breaking the notion of the angular filter of ENZ metamaterials, should readily be applied to other extreme-parameter materials and pave the way to explore more unexpected transmission properties of these metamaterials.

Broadband Non-volatile Photonic Switching Based on Optical Phase Change Materials -- Beyond the Classical Figure-of-Merit

Yifei Zhang, Juejun Hu, Qihang Zhang, Junying Li, Richard Soref, and Tian Gu

Doc ID: 312323 Received 31 Oct 2017; Accepted 22 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: In this letter, we propose and theoretically analyze a broadband, non-volatile on-chip switch design in the telecommunication C-band with record low loss and crosstalk. The unprecedented device performance builds on two key innovations: 1) a new optical phase change material (O-PCM) Ge2Sb2Se4Te1 (GSST), which exhibits significantly reduced optical attenuation compared to traditional O-PCMs; and 2) a non-perturbative design which enables low-loss device operation beyond the classical figure-of-merit (FOM) limit. We further demonstrate that the 1-by-2 and 2-by-2 switches can serve as basic building blocks to construct non-blocking and non-volatile on-chip switching fabric supporting arbitrary numbers of input and output ports.

CEP dependence of Signal and Idler upon Pump-Seed synchronization in optical parametric amplifiers

Giulio Maria Rossi, Lu Wang, Roland Mainz, Huseyin Cankaya, Giovanni Cirmi, and Franz Kaertner

Doc ID: 307051 Received 13 Sep 2017; Accepted 22 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: We present a comprehensive study of the effect of Pump-Seed timing fluctuations on the carrier-envelope phase (CEP) of Signal and Idler pulses emerging from an OP(CP)A. A simple analytical model is derived in order to provide an intuitive explanation of the origin of CEP fluctuations, while split-step simulations are performed to cover a broad range of different seeding schemes. Finally we compare the simulation results with real observations of the CEP of the Idler pulses generated by an OPA. The quantitative model presented provides a key tool for designing next generation of low noise CEP-stable OP(CP)A-based sources.

Localized Excitation of Polarized Light Emission by Cathodeluminescence Spectroscopy

Yuhui Hu, Fei Chen, Yajun Gao, Xiang Xiong, Ruwen Peng, and Mu Wang

Doc ID: 312974 Received 08 Nov 2017; Accepted 21 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: Surface plasmons, the resonance of free electrons on the metal-air interface, may strongly interact with light and generate some extraordinary optical effects. Instead of using conventional planar light excitation, here we excite surface plasmons with focused electron beam on metallic nanostructures with different geometrical symmetry. With the help of polarizer and filter in the detection system, we obtain cathodeluminescence (CL) images with different polarization at certain wavelength. The maxima in the CL images show that the focused electron beam may efficiently excite luminescence with different polari- zation at different spots. Comparing with the data collected on the structures with specific geometrical symmetry, we demonstrate that the polarization of the emitted light depends on both the structural symmetry and the excitation location. We suggest that this work is enlightening to understand the relationship between surface plasmon resonance on the structure and emi- ssion of CL with different polarizations.

Visible Light Optical Coherence Microscopy of the Brain with Isotropic Femtoliter Resolution In Vivo

Conrad Merkle, Shau Poh Chong, Aaron Kho, Jun Zhu, Alfredo Dubra, and Vivek Srinivasan

Doc ID: 308468 Received 02 Oct 2017; Accepted 21 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Most flying-spot Optical Coherence Tomography (OCT) and Optical Coherence Microscopy (OCM) systems use a symmetric confocal geometry, where the detection path retraces the illumination path starting from and ending with the spatial mode of a single mode optical fiber. Here, we describe a visible light OCM instrument that breaks this symmetry to improve transverse resolution without sacrificing collection efficiency. This was achieved by overfilling a water immersion objective on the illumination path, while maintaining a conventional Gaussian mode detection path (1/e2 intensity diameter ~0.82 Airy disks), enabling ~1.1 μm full-width at half-maximum (FWHM) transverse resolution. At the same time, a ~0.9 μm FWHM axial resolution in tissue, achieved by a broadband visible light source, enabled femtoliter volume resolution. We characterized this instrument according to paraxial coherent microscopy theory, and finally, used it to image the meningeal layers, intravascular red blood cell-free layer, and myelinated axons in the mouse neocortex in vivo through the thinned skull.

Magnetometry using fluorescence of sodium vapor

Tingwei Fan, Lei Zhang, Xuezong Yang, Shenzhen Cui, Tianhua Zhou, and Yan Feng

Doc ID: 307515 Received 20 Sep 2017; Accepted 21 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: Magnetic resonance of sodium fluorescence is studied with varying laser intensity, duty cycle, and field strength. A magnetometer based on sodium vapor cell filled with He buffer gas is demonstrated, which uses a single amplitude-modulated laser beam. With a 589 nm laser tuned at D1 or D2 line, the magnetic field is inferred from the variation of fluorescence. A magnetic field sensitivity of 150 pT/√Hz is achieved at D1 line. The work is an important step towards sensitive remote magnetometry with mesospheric sodium.

Phase modulator mode based on pre-transitional effect of antiferroelectric liquid crystals

Ken Ishikawa and Zhengyu Feng

Doc ID: 312468 Received 02 Nov 2017; Accepted 21 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: We demonstrate a novel phase only modulation mode based on the pre-transitional effect of the antiferroelectric liquid crystal. 2 pi phase modulation without changing the polarization state of the incident light is achieved with a low field(1.8 V/mm). This phase modulation mode also shows ultrafast response time(less than 300 microseconds) and a uniform optical texture with easy fabrication process. This phase modulator can be applied to laser beam steering, virtual reality and hologram etc. in the future.

Continuous-wave induced resonant spectral sidebands in soliton fiber lasers

Xuewen Shu and Du Yueqing

Doc ID: 312548 Received 03 Nov 2017; Accepted 21 Nov 2017; Posted 11 Dec 2017  View: PDF

Abstract: We observed the resonant sidebands similar to the Kelly sidebands but caused by the coupling between continuous-wave and dispersive waves in a mode-locked ring fiber laser for the first time. The coupling between the continuous-wave and dispersive waves is a linear process, which is different from the previously observed parametric sub-sidebands. Regimes of the continuous-wave induced sidebands are discussed. Experimental results agree both qualitatively and quantitatively well with theoretical analysis. The results enrich the nonlinear dynamics of ultrafast fiber lasers and may have potential in optically controlling mode-locked lasers.

Efficient diode-pumped Er:KLu(WO4)2 laser at ~1.61 µm

Josep Maria Serres, Pavel Loiko, Venkatesan Jambunathan, Xavier Mateos, Vladimir Vitkin, Antonio Lucianetti, Tomas Mocek, Magdalena Aguilo, Francesc Diaz, Uwe Griebner, and Valentin Petrov

Doc ID: 309941 Received 25 Oct 2017; Accepted 19 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: We report on an efficient diode-pumped continuous-wave Erbium-doped monoclinic double tungstate laser. It is based on a 1 at.% Er3+:KLu(WO4)2 (Er:KLuW) crystal cut along the Ng optical indicatrix axis. The Er:KLuW microchip laser, diode-pumped at 0.98 µm, generates 268 mW at 1.610 µm with a slope efficiency of 30%. The output is linearly polarized (E || Nm) and the laser beam is nearly diffraction-limited. Spectroscopic properties of Er3+ in KLuW are also presented. The maximum σSE = 3.0×10-20 cm2 is at ~1.535 µm for E || Nm. The microchip Er:KLuW laser outperforms the commercial Er,Yb:glass.

Intensity modulation of a terahertz bandpass filter: utilizing image currents induced on MEMS reconfigurable metamaterials

Fangrong HU, yixing fan, Xiaowen Zhang, wenying jiang, YUANZHI CHEN, Li Peng, xianhua yin, and Wentao Zhang

Doc ID: 309927 Received 25 Oct 2017; Accepted 19 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We experimentally demonstrated a tunable terahertz (THz) bandpass filter based on microelectromechanical systems (MEMS) reconfigurable metamaterials (MMs). The unit cell of the filter consists of two split-ring-resonators (SRRs) and a movable bar. Initially, the movable bar situates at the center of the unit cell and the filter has two passbands whose central frequencies locating at 0.65 THz and 0.96 THz, respectively. The intensity of two passbands can be actively modulated by the movable bar, and a maximum modulation depth of 96% is achieved at 0.96 THz. The mechanism of tunability is investigated using the finite-integration-time-domain (FITD) method. The result shows that the image currents induced on the movable bar are opposite to the resonance currents induced on the SRRs, and thus weakens the oscillating intensity of the resonance currents. This scheme paves a way to dynamically control and switch the THz wave at some constant frequencies utilizing induced image currents.

Kilohertz binary phase modulator for pulsed laser sources using a digital micromirror device

Maximilian Hoffmann, Ioannis Papadopoulos, and Benjamin Judkewitz

Doc ID: 309467 Received 19 Oct 2017; Accepted 16 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: The controlled modulation of an optical wavefront is required for aberration correction, digital phase conjugation or patterned photostimulation. For most of these applications it is desirable to control the wavefront modulation at the highest rates possible. The digital micromirror device (DMD) presents a cost-effective solution to achieve high-speed modulation and often exceeds the speed of the more conventional liquid crystal spatial light modulator, but is inherently an amplitude modulator. Furthermore, spatial dispersion caused by DMD diffraction complicates its use with pulsed laser sources, such as those used in nonlinear microscopy. Here we introduce a DMD-based optical design that overcomes these limitations and achieves dispersion-free high-speed binary phase modulation. We show that this phase modulation can be used to switch through binary phase patterns at the rate of 20 kHz in two-photon excitation fluorescence applications.

Nonlinearity-aware 200-Gbit/s discrete multi-tone transmission for C-band short-reach optical interconnects with a single packaged EML

Lu Zhang, Xuezhi Hong, Xiaodan Pang, Oskars Ozolins, Aleksejs Udalcovs, Richard Schatz, Changjian Guo, Junwei Zhang, FREDRIK NORDWALL, Klaus Engenhardt, Urban Westergren, Sergei Popov, GUNNAR JACOBSEN, shilin xiao, Weisheng Hu, and Jiajia Chen

Doc ID: 306205 Received 01 Sep 2017; Accepted 13 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: We experimentally demonstrate the transmission of 200-Gbit/s discrete multi-tone (DMT) at soft-FEC limit in an intensity-modulation direct-detection system with a single C-band packaged distributed feedback laser and traveling-wave electro absorption modulator (DFB-TWEAM), digital-to-analog converter (DAC) and photodiode. The bits and power loaded DMT signal is transmitted over 1.6 km standard single mode fiber (SSMF) with a net rate of 166.7-Gbit/s, achieving an effective electrical spectrum efficiency of 4.93 bit/s/Hz. Meanwhile, net rates of 174.2-Gbit/s and 179.5-Gbit/s are also demonstrated over 0.8km SSMF and in optical back-to-back case, respectively. The feature of the packaged DFB-TWEAM is presented. The nonlinearity-aware digital signal processing algorithm for channel equalization is mathematically described, which improves the signal-to-noise ratio up to 4 dB.

Two-mode surface plasmon lasing in hexagonal arrays

Vasco Tenner, Michiel de Dood, and Martin van Exter

Doc ID: 297731 Received 25 Aug 2017; Accepted 12 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: We demonstrate surface-plasmon lasing in hexagonal metal hole arrays with a semiconductor gain medium. The device can be tuned between two laser modes, with distinct wavelengths, spatial distributions and polarization patterns by changing the size of the optically pumped area. One of the modes exhibits a six-fold polarization pattern, while the mode observed for larger pump spots has a rotationally symmetric polarization pattern. We explain the mode tuning by the differences of in-plane and radiative out-of-plane losses of the modes. The spatial and polarization properties of the modes are conveniently described by a sum of vectorial OAM beams with orbital, spin and total angular momentum j = l+s.

Homographically generated light-sheets for themicroscopy of large specimens

Craig Russell, Eric Rees, and Clemens Kaminski

Doc ID: 304060 Received 29 Sep 2017; Accepted 12 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: We compare the performance of linear and nonlinear methods for aligning the excitation and detection planes throughout large specimen volumes in digitally scanned light sheet microscopy. An effective non-linear method involves registering four corner extrema of the imaging volume using a projective transform. We show this improves on the light collection efficiency of a 3-point affine registration by an average of 42% over a typical specimen volume, but increasingly higher-order corrections provide more modest returns. The accuracy of illumination/detection registration methods are now very pertinent to biological research in view of current trends towards imaging large or expanded samples, at depth, with diffraction limited resolution.

Effects of defocus on the transfer function of coherence scanning interferometry

Rong Su, MATTHEW THOMAS, Richard Leach, and Jeremy Coupland

Doc ID: 304940 Received 17 Aug 2017; Accepted 06 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: Coherence scanning interferometry (CSI) offers three dimensional (3D) measurement of surface topography with high precision and accuracy. Defocus within the interferometric objective lens, however, is commonly present in CSI measurements, and reduces both the resolving power of the imaging system and the ability to measure tilted surfaces. This paper extends the linear theory of CSI to consider the effects of defocus on the 3D transfer function and the point spread function in an otherwise ideal CSI instrument. The results are compared with measurements of these functions in a real instrument. This work provides further evidence for the validity of the linear systems theory of CSI.

An inclined emitting slotted single mode laser with 1.7 degree vertical divergence angle for PIC applications

Yejin Zhang, Yanmei Su, Yu Bi, Jiaoqing Pan, Hongyan Yu, yang zhang, Jie Sun, xinyan sun, and Ming Chong

Doc ID: 306547 Received 06 Sep 2017; Accepted 11 Oct 2017; Posted 30 Nov 2017  View: PDF

Abstract: In this letter, a new type of single mode slotted laser used for on-chip light source in photonic integrated circuits is proposed. An inclined light beam with a low vertical divergence angle can be directly coupled into the surface grating of the silicon to form an integrated light source. Experimentally, an III-V laser with a 54.6 degree inclined angle and a vertical divergence angle of 1.7 degree is achieved by introducing a kind of specially distributed micro-structure. The side mode suppression ratio is better than 45 dB and the continuous wave output power reaches 6.5 mW at room temperature. We report the inclined emitting micro-structured single mode laser with a low divergence angle for the first time.

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