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Accepted papers to appear in an upcoming issue

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Topology-optimized multi-track ring resonators and 2D microcavities for nonlinear frequency conversion

Zin Lin, Marko Loncar, and Alejandro Rodriguez

Doc ID: 290663 Received 14 Apr 2017; Accepted 23 Jun 2017; Posted 23 Jun 2017  View: PDF

Abstract: We exploit recently developed topology-optimization techniques to design complex, wavelength-scale resonators for enhancing various nonlinear $\chi^{(2)}$ and $\chi^{(3)}$ frequency conversion processes. In particular, we demonstrate aperiodic, multi-track ring resonators and 2D slab microcavities exhibiting long lifetimes $Q \gtrsim 10^4$, small modal volumes $V \gtrsim (\lambda/2n)^3$, and among the largest nonlinear overlaps (a generalization of phase matching in large-etalon waveguides) possible, paving the way for efficient, compact, and wide-bandwdith integrated nonlinear devices.

High-average-power femtosecond laser at 258 nm

Michael Müller, Arno Klenke, Thomas Gottschall, Robert Klas, Carolin Rothhardt, Stefan Demmler, Jan Rothhardt, Jens Limpert, and Andreas Tünnermann

Doc ID: 291640 Received 30 Mar 2017; Accepted 22 Jun 2017; Posted 23 Jun 2017  View: PDF

Abstract: We present an ultrafast fiber laser system delivering 4.6 W average power at 258 nm based on two-stage fourth-harmonic generation in beta barium borate (BBO). The beam quality is close to diffraction limited with an M2-value of 1.3 x 1.6. The pulse duration is 150 fs, which potentially is compressible down to 40 fs. A plain BBO and a Sapphire-BBO compound are compared with respect to the achievable beam quality in the conversion process. This laser is applicable in scientific and industrial fields. Further scaling to higher average power is discussed.

Polarization-dependent strong coupling between surface plasmon polaritons and excitons in an organic-dye-doped nanostructure

Kun Zhang, Tianyong Chen, Wenbo Shi, Cheng-Yao Li, Ren-Hao Fan, Qian-Jin Wang, Ruwen Peng, and Mu Wang

Doc ID: 295991 Received 16 May 2017; Accepted 20 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: In this work, we demonstrate polarization-dependent strong coupling between surface plasmon polaritons (SPPs) and excitons in the J-aggregates attached aperture array. It is shown that the excitons strongly couple with the polarization-dependent SPPs, and Rabi splittings are consequently observed. As a result, the polarization-dependent polariton bands are generated in the system. With increasing the incident angle, the polaritons disperse to higher energies under transverse-electric (TE) illumination; while the polaritons disperse to lower energies under transverse-magnetic (TM) illumination. Therefore at different polarization incidence, we experimentally achieve distinct polaritons with opposite group velocities. In this way, by tuning the polarization of the incident light, we can excite different polaritons whose energy propagating to opposite directions. Furthermore, by retrieving the mixing fractions of the components in these polariton bands, we find that the dispersion properties of the polaritons inherit from both the SPPs and excitons. Our investigation may inspire related studies on tunable photon-exciton interactions and achieve some potential applications on active polariton devices.

High-efficiency broadband excitation and propagation of second-mode spoof surface plasmon polaritons by complementary structure

Dawei Zhang, Kuang Zhang, Qun Wu, Guohui Yang, and xuejun sha

Doc ID: 296739 Received 26 May 2017; Accepted 20 Jun 2017; Posted 20 Jun 2017  View: PDF

Abstract: A complementary structure based on coplanar waveguides (CPWs) with periodical etching slots is proposed to support spoof surface plasmon polaritons (SSPPs). In contrast to the traditional slotline-based complementary SSPP structure, dispersion curve of the second mode by the proposed structure has a much lower starting point from the origin which exhibits greatly improved operating bandwidth. Moreover, tighter confinements of SSPPs in the region of small wave vectors corresponding to lower frequencies can be predicted from the dispersion analysis, which means enhancement of transmission efficiency. Then a simple and efficient transition structure with tapered CPWs and gradient slots is proposed to realize high-efficiency and broadband excitation of the second mode of SSPPs for the first time. Based on the proposed structure, seamless connection between CPWs and SSPP structure can be achieved. A prototype is fabricated to experimentally validate the high efficiency and broadband features of the second-mode excitation and propagation of SSPPs. The proposed structure can promote the development of plasmonic integrate circuits and functional devices at microwave frequencies.

Octave-spanning supercontinuum generation in a silicon-rich nitride waveguide: erratum

Xing Liu, Minhao Pu, Binbin Zhou, Clemens Krueckel, Attila Fulop, Victor Torres-Company, and Morten Bache

Doc ID: 298041 Received 19 Jun 2017; Accepted 20 Jun 2017; Posted 23 Jun 2017  View: PDF

Abstract: We update the simulations presented in Opt. Lett. 41, 2719 (2016) using a corrected value for the material nonlinearity.

A high-energy Nd:YAG laser system with arbitrarysub-nanosecond pulse shaping capability

Randy Meijer, Aneta Stodolna, Stefan Witte, and Kjeld Eikema

Doc ID: 295757 Received 15 May 2017; Accepted 19 Jun 2017; Posted 20 Jun 2017  View: PDF

Abstract: We report on a laser system capable of generating high-energy (>270 mJ) temporally shaped pulses at 1064 nm with 0.43 ns shaping resolution. The pulses are generated by modulation of a continuous wave seed laser, and subsequent amplification by a dual-stage grazing incidence Nd:YVO4 'bounce' amplifier and a Nd:YAG power amplifier (all quasi-continuous diode-pumped). The system produces pulses with a high-quality top-hat spatial beam profile, up to 0.6 GW of peak power, a power stability of 0.22% rms, and fully programmable complex temporal shapes.

Broadband etching-free metal grating couplersembedded in titanium dioxide waveguides

Manon Lamy, Kamal Hammani, Juan Arocas, Christophe Finot, and Jean-Claude Weeber

Doc ID: 292534 Received 12 Apr 2017; Accepted 19 Jun 2017; Posted 20 Jun 2017  View: PDF

Abstract: Embedded metal grating couplers into titanium dioxidelayer are proposed. A coupling efficiency better than20 % is experimentally demonstrated with a 3-dBbandwidth of 86 nm in agreement with simulationresults. This allowed us to perform error-freetransmissions of 10 Gbit/s wavelength multiplexedsignals in the C-band.

Entanglement in four-wave mixing process

zhan Zheng, Hailong Wang, Bing Cheng, and Jietai Jing

Doc ID: 293265 Received 21 Apr 2017; Accepted 19 Jun 2017; Posted 20 Jun 2017  View: PDF

Abstract: We investigate different kinds of entanglement in a four-wave mixing process with a degenerate pump. After analyses on means and quantum fluctuations of the three output beams (Stokes, anti-Stokes, and pump), we verify the existence of genuine tripartite entanglement, and quantify bipartite, two-mode, as well as tripartite entanglement with the covariance matrix. We find out that the input pump power and the nonlinear coupling strength are the physical origins to enhance entanglement at a given photon-loss.

Photonic RF mixer for phase-coded signal generation using a silicon microring modulator

yiwei Xie, Leimeng Zhuang, and Arthur Lowery

Doc ID: 295117 Received 08 May 2017; Accepted 19 Jun 2017; Posted 20 Jun 2017  View: PDF

Abstract: Phase-coded radio frequency (RF) pulses are widely adopted for radar systems as an effective signal format to enable high range resolution. However, generating such signals conventionally requires high-speed electronics and complex RF circuitry that impose burdens on the system cost and power consumption. In particular, modern radar systems desire features such as high frequencies, e.g. in the millimeter-wave region, high compactness, and high system flexibility, which pose great challenges for the conventional all-electronics solutions. In contrast, integrated microwave photonics opens a path to solutions that are able to provide those features simultaneously, together with potential for full integration and low cost fabrication. Here, we present an integrated microwave photonic implementation of a binary-phase-coded millimeter-wave signal generation. The core device is a silicon microring modulator with a device size of 0.13 × 0.32 mm2 and a modulation bandwidth of GHz. Using RF seed frequencies of 17.5 GHz and 20 GHz, respectively, we experimentally demonstrated the generation of binary-phase-coded signals at 35 GHz and 40 GHz using our proposed approach, the performance of which was verified by a pulse compression ratio of 94 and 106, respectively. The result of this work points to the realization of a chip-scale flexible millimeter-wave signal generator.

Lens-free all-fiber probe with an optimized output beam for optical coherence tomography

Zhihua Ding, Jianrong Qiu, shen yi, Zhiyan Chen, and Wen Bao

Doc ID: 296390 Received 23 May 2017; Accepted 19 Jun 2017; Posted 23 Jun 2017  View: PDF

Abstract: A high efficiency lens-less all-fiber probe for optical coherence tomography (OCT) is presented. The probe is composed of a segment of large-core multimode fiber (MMF), a segment of tapered MMF and a length of single-mode fiber (SMF). Controllable output beam can be designed by simply adjustment of its probe structure parameters (PSPs) instead of selection of fibers with different optical parameters. A side-view probe with a diameter of 340 µm and a rigid length of 6.37 mm was fabricated, which provides an effective imaging range of ~0.6 mm with a FWHM beam diameter of less than 30 μm. The insertion loss of the probe was measured to be 0.81 dB, ensuring a high sensitivity of 102.25 dB. Satisfactory images were obtained by the probe-based OCT system, demonstrating the feasibility of the probe for endoscopic OCT applications.

Competition between Raman and Kerr effects in microresonator comb generation

Yoshitomo Okawachi, Mengjie Yu, Vivek Venkataraman, Pawel Latawiec, Austin Griffith, Michal Lipson, Marko Loncar, and Alexander Gaeta

Doc ID: 295350 Received 08 May 2017; Accepted 19 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: We investigate the effects of Raman and Kerr gain in crystalline microresonators and determine the conditions required to generate modelocked frequency combs. We show theoretically that strong, narrowband Raman gain determines a maximum microresonator size allowable to achieve comb formation. We verify this condition experimentally in diamond and silicon microresonators and show that there exists a competition between Raman and Kerr effects that leads to the existence of two different comb states.

Design rules for combined label-free and fluorescence Bloch surface wave biosensors

Francesco Michelotti, Riccardo Rizzo, Alberto Sinibaldi, Peter Munzert, Christoph Wächter, and Norbert Danz

Doc ID: 295409 Received 10 May 2017; Accepted 19 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: We report on the fabrication and physical characterization of optical biosensors implementing simultaneous label-free and fluorescence detection and taking advantage of the excitation of Bloch surface waves at a photonic crystal’s truncation interface. Two types of purposely-designed one dimensional photonic crystals on molded organic substrates with micro-optics were fabricated. These feature either high or low finesse of the Bloch surface wave resonances and were tested on the same optical readout system. The experimental results show that designing biochips with a large resonance quality factor does not necessarily lead in the real case to an improvement of the biosensor performance. Conditions for optimal biochips’ design and operation of the complete bio-sensing platform are established.

On-chip Reconfigurable Optical Add-Drop Multiplexer for Hybrid Wavelength/Mode-Division-Multiplexing Systems

Wang Shipeng, Xianglian Feng, Shiming Gao, Yaocheng Shi, Tingge Dai, hui Yu, Hon Tsang, and Daoxin Dai

Doc ID: 294619 Received 25 Apr 2017; Accepted 18 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: A silicon-based on-chip ROADM is proposed and demonstrated for hybrid WDM-MDM systems for the first time. The present ROADM consists of a four-channel mode demultiplexer, four wavelength-selective thermo- optic switches based on micro-ring resonators, and a four-channel mode multiplexer. With the present ROADM, one can add/drop any wavelength-channel of any mode to/from the multimode bus waveguide successfully with an excess loss of 2~8 dB and an extinction ratio of ~20 dB over a wavelength range of 1525~1565 nm.

Plasmonic nanohole electrodes for active color tunableliquid crystal transmissive pixels

Richard Bartholomew, Calum Williams, Richard Bowman, Ammar Khan, and Timothy Wilkinson

Doc ID: 293345 Received 26 Apr 2017; Accepted 18 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: Plasmonic pixels have been shown to offer numerous advantages over pigment-based color filters used in modern commercial liquid crystal (LC) displays. However, wideband dynamic tunability across the visible spectrum remains challenging. We experimentally demonstrate transmissive electrically tunable LCnanohole pixels operating across the visible spectrum with unpolarized input light. An ultrathin Al nanohole electrode is designed to exhibit a polarized spectral response based on surface plasmon resonances. An output analyzer in combination with a nematic LC layer enables pixel color to be electronically controlled through an applied voltage across the device. Where LC reorientation leads to tunable mixing of the relative contributions from the plasmonic color input. The nanostructured Al layer, acting as combined electrode, polarizer and functional color filter, is highly promising for electro-optic display applications.

Tunable coupling-induced resonance splitting in self-coupled Silicon ring cavity with robust spectral characteristics

Awanish Pandey and Shankar Kumar Selvaraja

Doc ID: 295626 Received 09 May 2017; Accepted 17 Jun 2017; Posted 23 Jun 2017  View: PDF

Abstract: We propose and demonstrate a self-coupled micro ring resonator for resonance splitting by mutual mode coupling of cavity mode and counter-propagating mode in Silicon-on-Insulator platform The resonator is constructed with a self-coupling region that can excite counter-propagating mode. We experimentally study the effect of self-coupling on the resonance splitting, resonance extinction, and quality-factor evolution and stability. Based on the coupling,we achieve 72%of FSR splitting for a cavity with FSR 2.1 nm with < 5% variation in the cavity quality factor. The self-coupled resonance splitting shows highly robust spectral characteristic that can be exploited for sensing and optical signal processing.

Coexistence of cavity solitons with different polarization states and different power peaks in all fiber resonators

Etienne Averlant, Mustapha Tlidi, Krassimir Panajotov, and Lionel Weicker

Doc ID: 295109 Received 08 May 2017; Accepted 17 Jun 2017; Posted 20 Jun 2017  View: PDF

Abstract: We theoretically investigate a weakly birefringent all fiber cavity subject to linearly polarized optical injection. We describe the propagation of light inside the cavity using, for each linear polarization component of the electric field, the Lugiato-Lefever model. These two components are coupled by cross-phase modulation. We show that, for a wide range of parameters,there is a coexistence between a homogeneous steady state and two different types of temporal vector cavity solitons, which can be hosted in the same system. They differ by their polarization state and peak intensity. Weconstruct their bifurcation diagram and show that they are connected through a saddle-node bifurcation. Finally, we show that vector cavity solitons exhibit multistability involving different polarization states withdifferent energies.

Orbital Angular Momentum Beams Generated by Passive Dielectric Phase Masks and Their Performance in a Communication Link

Guodong Xie, Zhe Wang, Yan Yan, Amir Arbabi, Cong Liu, Zhe Zhao, Yongxiong Ren, Long Li, Nisar Ahmed, Asher Willner, Ehsan Arbabi, Andrei Faraon, Robert Bock, Solyman Ashrafi, Moshe Tur, and Alan Willner

Doc ID: 296912 Received 29 May 2017; Accepted 16 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: We demonstrate the generation of orbital angular momentum beams using high-efficient polarization-insensitive phase masks. The OAM beams generated by the phase masks are characterized in terms of their tolerance to misalignment (lateral displacement or tilt) between the incident beam and phase mask. For certain scenarios, our results show that (a) when the tilt angle is within the range of -20 to +20 degrees, the crosstalk among modes is less than -15 dB; and (b) lateral displacement of 0.3 mm could cause a large amount of power leaked to adjacent modes. Finally, OAM beams generated by the phase masks are demonstrated over a 2-channel OAM-multiplexing link, where each channel carries a 40 Gbit/s data stream. An optical signal to noise ratio (OSNR) penalty of ~1 dB is measured without crosstalk at the bit error rate (BER) of 3.8e-3. With crosstalk, an OSNR penalty of < 1.5 dB is observed at the same BER.

A portable spectrometer for airborne and ground-based remote sensing of geological CO2 emissions

Manuel Queisser, Mike Burton, Antonio Chiarugi, and Graham Allan

Doc ID: 292791 Received 27 Apr 2017; Accepted 16 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: A man-portable, dispersive, CW, laser-based remote-sensing spectrometer with a ~2 km range has been developed for the ERC project CO2Volc. The instrument demonstrated its flexibility in measuring both atmospheric column CO2 from an airborne platform and terrestrial emission of CO2 from a remote mud-volcano, Bledug Kuwu, Java, Indonesia from a ground-based sight. This system scans the CO2 absorption line with 20 discrete wavelengths as opposed to the typical two wavelength online offline instrument. This multi-wavelength approach offers an effective quality-control, bias-control and confidence-estimate of measured CO2 concentrations via spectral fitting. The simplicity, ruggedness and flexibility in the design allows for easy transportation, use on different platforms with quick setup and operation in some of the most challenging climatic conditions. The results represent a step-stone towards widespread use of active one-sided gas remote sensing in the Earth sciences.

Femtosecond laser written waveguides deep inside silicon

F Omer Ilday, Ihor Pavlov, Onur Tokel, Viktor Kadan, Ghaith Makey, Ahmet Turnali, Özgün Yavuz, and Svitlana Pavlova

Doc ID: 294915 Received 28 Apr 2017; Accepted 16 Jun 2017; Posted 16 Jun 2017  View: PDF

Abstract: Photonic devices that can guide, transfer or modulate light are highly desired in electronics and integrated silicon photonics. Here, we demonstrate for the first time, to the best of our knowledge, creation of optical waveguides deep inside silicon using femtosecond pulses at a central wavelength of 1.5 $\mu$m. To this end, we use 350-fs-long, 2-$\mu$J pulses with a repetition rate of 250 kHz from an Er-doped fiber laser, which we focused inside silicon to create permanent modifications of the crystal. The position of the beam is accurately controlled with pump-probe imaging during fabrication. Waveguides of 5.5 mm length, and 20 $\mu$m diameter were created by scanning the focal position along the beam propagation axis. The fabricated waveguides were characterized with a continuous-wave laser operating at 1.5 $\mu$m. The refractive index change inside the waveguide was measured with optical shadow-graphy, yielding a value of $6 \times 10^{-4}$; as well as by direct light coupling and far-field imaging, yielding a value of $3.5 \times 10^{-4}$. The formation mechanism of the modification is discussed.

Complex decorrelation averaging in optical coherence tomography: A way to reduce the effect of multiple scattering and improve image contrast in a dynamic scattering medium

Lars Thrane, Shi Gu, Brecken Blackburn, Kishore Damodaran, Andrew Rollins, and Michael Jenkins

Doc ID: 294533 Received 08 May 2017; Accepted 14 Jun 2017; Posted 16 Jun 2017  View: PDF

Abstract: We demonstrate that complex decorrelation averaging can reduce the effect of multiple scattering and improve OCT imaging contrast. Complex decorrelation averaging calculates the product of an A-scan and the complex conjugate of a subsequent A-scan. The resultant signal is the product of the amplitudes and the phase difference. All these resulting complex signals at a particular location are then averaged. We take advantage of the fact that complex averaging, in contrast to conventional magnitude averaging, is sensitive to phase decorrelation. Sample motion that increases signal phase variance results in lower signal magnitude after complex averaging. Such motion preferentially results in a faster decorrelation of the multiple scattering signal when compared to the single scattering signal with each scattering event spreading the phase. This indicates that we may reduce multiple scattering by implementing complex decorrelation averaging to preferentially reduce the magnitude of the multiply scattered light signal in OCT images. By adjusting the time between phase-differenced A-scans, one can regulate the amount of measured decorrelation. We have performed experiments on liquid phantoms that give experimental evidence for this hypothesis. A substantial improvement in OCT image contrast using complex decorrelation averaging is demonstrated.

Surface Nanoscale Axial Photonics at a capillary fiber

Misha Sumetsky, Tabassom Hamidfar, Artemiy Dmitriev, Brian Mangan, and Pablo Bianucci

Doc ID: 295540 Received 10 May 2017; Accepted 14 Jun 2017; Posted 16 Jun 2017  View: PDF

Abstract: We present the theory and first experimental demonstration of a sensing platform based on Surface Nanoscale Axial Photonics (SNAP) at a capillary fiber. The platform explores optical whispering gallery modes which circulate inside the wall of a capillary and slowly propagate along its axis. Due to the small thickness of the capillary wall, these modes are sensitive to spatial and temporal variations of refractive index of the media adjacent to the internal capillary surface. In particular, the developed theory allows to determine the internal effective radius variation of the capillary from the measured mode spectra. Experimentally, a SNAP resonator is created by local annealing of the capillary with a focused CO₂ laser followed by internal etching with hydrofluoric acid. The comparison of the spectra of this resonator in the cases when it is empty and filled with water allows us to determine the internal surface nonuniformity introduced by etching. The results obtained pave the way for a novel advanced approach in sensing of media adjacent to the internal capillary surface and, in particular, in microfluidic sensing.

Real-time fibre optic anemometer based on a laser-heated few layers graphene in an aligned graded index fibre

Ran Gao, Dan-feng Lu, Jin Cheng, and Zhi-mei Qi

Doc ID: 293059 Received 26 Apr 2017; Accepted 14 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: A real-time all-fibre anemometer based on laser-heated few layer graphene in aligned graded index fibers has been proposed and experimentally demonstrated. The proposed fibre-optic anemometer was composed of a pair of all-fibre collimators by using aligned graded index fibers, which was coated with the few layer graphene. The few layer graphene was heated through a heating light from a 532 nm laser, which changed the optical transmittance of signal light with the wavelength of 1550 nm. The wind speed can be measured through the transmission power of the signal light based on the wind cooling effects on the heated few layer graphene, acting as a “hot-wire” anemometer. The experimental results show that the maximum sensitivity of the anemometer reaches -22.03 μW/(m/s), and a fast response time can be achieved as 0.064 s. The proposed fibre sensor can be used for the real-time measurement of wind speed in the fields of environmental monitoring, oil exploration, oceanography research, etc.

Real-time On-line Photonic Random Number Generation

Pu Li, Jianguo Zhang, sang xiao, Xianglian Liu, Yanqiang Guo, Xiaomin Guo, Anbang Wang, K. Alan Shore, and Yun-cai Wang

Doc ID: 295721 Received 11 May 2017; Accepted 14 Jun 2017; Posted 20 Jun 2017  View: PDF

Abstract: We present a real-time scheme for ultrafast random number extraction from an broadband photonic entropy source. Ultralow jitter mode-locked pulses are used to sample the stochastic intensity fluctuations of the entropy source in the optical domain. A discrete self-delay comparison technology is exploited to quantize the sampled pulses into continuous random number streams directly. This scheme is bias-free and both eliminates the electronic jitter bottleneck confronted by currently available physical random number generators and has no need for threshold-tuning and post-processing. To demonstrate its feasibility, we perform a proof of principle experiment using an optically injected chaotic laser diode. Random number streams at up to 7 Gb/s with verified randomness were thereby successfully extracted in real time. With the provision of a photonic entropy source with sufficient bandwidth, the present approach is expected to provide random number generation rates of several tens of Gb/s.

Bragg grating inscription in PMMA optical fibers using 400 nm femtosecond pulses

Christophe Caucheteur, Xuehao Hu, Damien Kinet, Karima Chah, Chi Fung PUN, and Hwa Yaw Tam

Doc ID: 294743 Received 01 May 2017; Accepted 14 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: In this letter, we report the fast growth of high quality uniform Bragg gratings in trans-4-stilbenemethanol (TS)-doped poly(methyl methacrylate) (PMMA) step-index optical fibers. Grating manufacturing was obtained using a 400 nm femtosecond pulsed laser and a 1060-nm-period uniform phase mask. For a 20 mW mean laser beam power, the grating reflectivity reaches 98 % in ~60 seconds. Our experimental results confirm that the FBG inscription process has a very high efficiency.

Optical Heterodyne-Enhanced Chirped Laser Dispersion Spectroscopy

Genevieve Plant, Yifeng Chen, and Gerard Wysocki

Doc ID: 295883 Received 26 May 2017; Accepted 13 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: A proof of concept heterodyne-enhanced chirped laser dispersion spectroscopy system is presented. In remote sensing systems where low return powers are expected, the addition of an optical local oscillator and subsequent non-linear processing can provide improved performance in chirped laser dispersion spectroscopy. Details about the system configuration, phase noise cancellation, and experimental verification are discussed.

Tunable higher-order orbital angular momentum using polarization-maintaining fiber

Brendan Heffernan, Robert Niederriter, Mark Siemens, and Juliet Gopinath

Doc ID: 294596 Received 25 Apr 2017; Accepted 13 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: For the first time, light with orbital angular momentum (OAM) of ±𝟐ℏ per photon is produced using commercially available polarization-maintaining fiber with modal purity > 96%. Twist measurements demonstrate that the average orbital angular momentum can be continuously tuned between ±𝟐ℏ. The authors consider beams of non-integer OAM, created using the presented method, as superpositions of integer OAM states.

Coherent Field Transients below 15 THz from Phase-Matched Difference Frequency Generation in 4H-SiC

Marco Patrick Fischer, Johannes Bühler, Gabriel Fitzky, Takayuki Kurihara, STEFAN EGGERT, Alfred Leitenstorfer, and Daniele Brida

Doc ID: 295576 Received 11 May 2017; Accepted 13 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: We experimentally demonstrate tunable, phase-matched difference frequency generation covering the spectral region below 15 THz using 4H-SiC as nonlinear crystal. This material combines a non-centrosymmetric lattice and strong birefringence with broadband transparency at low optical frequencies. Thorough refractive index measurements in the terahertz spectral range allow us to calculate phase-matching conditions for any near-infrared pump laser source. 4H-SiC is also exploited as detector crystal for electro-optic sampling. The results allow us to estimate the effective second-order nonlinear coefficient.

Versatile backconversion-inhibited broadband optical parametric amplification based on a idler-separated QPM configuration

Haizhe Zhong, Dianyuan Fan, Jianlong Yang, Shiwei Wang, and Ying Li

Doc ID: 297877 Received 12 Jun 2017; Accepted 13 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: Conversion efficiency and phase-matching (PM) bandwidth are both critical issues for broadband parametric processes. In some sense, they determine the highest peak power achieved via the optical parametric amplification (OPA). In this letter, a versatile idler-separated quasi-phase matching (QPM) scheme capable of both backconversion circumvention and ultra-broadband PM is presented. Full-dimension spatial-temporal simulations for the typical OPCPA processes at 800 nm and 3.4 μm were presented in detail. By virtue of the broad PM bandwidth on account of the non-collinear PM configuration, the backconversion circumvention on account of the idler-separated design, and the walk-off self-compensation on account of the symmetrical tilting grating patterns, significantly improved gain bandwidth, extremely high conversion efficiency and well-preserved beam profile are simultaneously achieved. Compared with the collinear configuration, the peak power can be potentially enhanced by 5-10 times under the same operation circumstances.

A wide wavelength tunable fast intensity-modulated light source for biophotonic applications

Ming-Che Chan, Tzu-Feng Huang, Sheng-Hao Tseng, and HSIEN-YI Wang

Doc ID: 286435 Received 15 Mar 2017; Accepted 13 Jun 2017; Posted 16 Jun 2017  View: PDF

Abstract: High modulation depth, fast (MHz to GHz), intensity-modulated light sources of various wavelengths within the 0.7-1.35 μm bio-penetration window are highly desirable for many bio-photonic diagnosis systems. In this work, we present a novel scheme for a wavelength tunable, ultra-broadband light source which simply consists of a pump laser, a nonlinear fiber, and demodulation circuits. The working wavelength range of the light source is from 0.7 to 1.35 μm which covers a large part of the bio-penetration window and its modulation frequencies extend from tens of MHz to the GHz range. The performance of the proposed light source in both the working wavelength range and modulation frequency bandwidth is much superior to that of any of the laser diodes and solid state lasers currently employed in the frequency domain and other bio-photonic applications. The results from our carefully designed diffused optical spectroscopy phantom measurement show the wide applicability of this novel light source for diverse bio-photonic applications.

Optical frequency comb generation with ultra-narrow spectral lines

Md Imrul Kayes and Martin Rochette

Doc ID: 292944 Received 26 Apr 2017; Accepted 12 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: We demonstrate an optical comb source that generates 550 ultra-narrow spectral lines with a spectral linewidth of 1.5-3 kHz, spanning over the C-band. The source originates from a single-mode Brillouin laser processed with phase modulation, pulse compression, and four-wave mixing. As a result, the narrow linewidth of the Brillouin laser improves the phase noise of every spectral line of the frequency comb.

Spectral stabilization of infrared frequency combs based on femtosecond optical parametric oscillators

Markku Vainio and Lauri Halonen

Doc ID: 295497 Received 08 May 2017; Accepted 12 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: Synchronously pumped optical parametric oscillator (SP-OPO) is one of the most common techniques to generate femtosecond frequency combs in the mid-infrared region. Stable long-term operation of an SP-OPO requires active locking of the OPO resonator round-trip time to the pump pulse interval. A simple modulation-free locking method based on stabilization of narrow-band frequency-doubled power of the SP-OPO output comb is demonstrated in this Letter. Since the frequency-doubled power strongly depends on the spectral shape of the comb, this new method leads to significantly better stability of the comb envelope spectrum than the commonly used dither-and-lock method.

Genetic algorithm-based control of birefringent filtering for self-tuning, self-pulsing fiber lasers

Robert Woodward and Edmund Kelleher

Doc ID: 287254 Received 22 Feb 2017; Accepted 12 Jun 2017; Posted 13 Jun 2017  View: PDF

Abstract: Polarization-based filtering in fiber lasers is well-known to enable spectral tunability and a wide range of dynamical operating states. This effect is rarely exploited in practical systems, however, because optimization of cavity parameters is non-trivial and evolves due to environmental sensitivity. Here, we report a genetic algorithm-based approach, utilizing electronic control of the cavity transfer function, to autonomously achieve broad wavelength tuning and the generation of Q-switched pulses with variable repetition rate and duration. The practicalities and limitations of simultaneous spectral and temporal self-tuning from a simple fiber laser are discussed, paving the way to on-demand laser properties through algorithmic control and machine learning schemes.

Freestanding dielectric nanohole array metasurface for mid-infrared wavelength applications

Junrong Ong, Hong-Son Chu, Valerian Chen, Alexander Zhu, and Patrice Genevet

Doc ID: 295843 Received 12 May 2017; Accepted 12 Jun 2017; Posted 13 Jun 2017  View: PDF

Abstract: We designed and simulated a freestanding dielectric optical metasurface based on arrays of etched nanoholes in a silicon membrane. We showed 2π phase control and high forward transmission at mid-infrared wavelengths around 4.2 μm by tuning the dimensions of the holes. We also identified the mechanisms responsible for high forward scattering efficiency and showed that these conditions are connected with the well-known Kerker conditions already proposed for isolated scatterers. A beam deflector was designed and optimizedthrough sequential particle swarm and gradient descent optimization to maximize transmission efficiency and reduce unwanted grating orders. Such freestanding silicon nanohole array metasurfaces are promising for the realization of silicon based mid-infrared optical elements.

Photonic jet: key role of injection for etchings with a shaped optical fiber tip

Robin Pierron, julien ZELGOWSKI, Pierre Pfeiffer, Joël Fontaine, and Sylvain Lecler

Doc ID: 292595 Received 19 Apr 2017; Accepted 12 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: We demonstrate the key role of the laser injection into a multimode fiber to obtain a photonic jet (PJ). PJ, a high concentrated propagating beam with a full width at half maximum smaller than the diffraction limit, is here generated with a shaped optical fiber tip using a pulsed laser source (1064 nm, 100 ns, 35 kHz). Three optical injection systems of light are compared. For similar etched marks on silicon with diameters around 1 μm, we show that the required ablation energy is minimum when the injected light beam is close to the fundamental mode diameter of the fiber. Thus, we confirm experimentally that to obtain a PJ out of an optical fiber, light injection plays a role as important as that of the tip shape, and therefore the role of the fundamental mode in the process.

Surface Plasmons in Nanostructured Black Phosphorus Flake

Xinyue Ni, Wang Lin, Jingxuan Zhu, Xiaoshuang Chen, and Wei Lu

Doc ID: 292964 Received 17 Apr 2017; Accepted 11 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: Recent re-discovered layered material-black phosphorous with a puckered honeycomb atomic structure, has experienced an upsurge in demand owing to its exotic physical properties such as layer-independent direct bandgap, linear dichroism etc. This paper presents plasmonic properties of the nano-structured BP flakes and its unprecedented capability of wide-band photon manipulation within the deep-subwavelength scale. Owing to its anisotropic characteristic in band-structure and moderate mobility, strong layer number and polarization dependences of the plasmon resonance with frequencies ranging from Infrared to terahertz has been found. Oblique plasmons have been observed in the square array of a BP flake, with the resonant frequency tuned in-situ either electrically or optically plus strong plasmon-induced absorption. Such advantages place BP as the best alternate candidate of plasmonic materials for ultra-scaled optoelectronic integration from terahertz to mid-infrared.

Tunable THz polariton laser based on 1342 nm wavelength for enhanced terahertz wave extraction

Andrew Lee, David Spence, and Helen Pask

Doc ID: 291527 Received 30 Mar 2017; Accepted 11 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: We detail the operation of a THz-laser source based on non-linear stimulated polariton scattering (SPS) in Mg:LiNbO3. This system utilizes a fundamental wavelength of 1342 nm to completely avoid the negative effect of free-carrier generation within high-resistivity silicon (Si) prisms, used to extract THz radiation from the Mg:LiNbO3 crystal. THz power of up to .6 μW (62.3 μW when chopped at 50% duty cycle) was detected at 1.33 THz, and frequency tunability across the range 1.05 – 2.2 THz was achieved.

2 W single longitudinal mode Yb:YAG DFB waveguide laser

Thomas Calmano, Martin Ams, Peter Dekker, Michael Withford, and Christian Kraenkel

Doc ID: 294592 Received 24 Apr 2017; Accepted 11 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: Single longitudinal mode (SLM) lasers are important tools for many scientific and commercial applications. SLM operation can be achieved in distributed feedback (DFB) lasers based on Bragg structures. Semiconductor waveguide DFB lasers are well established devices, but their output power is limited to a few hundred mW. DFB lasers have also been demonstrated in dielectric waveguides. However, in this case the output power was even lower. Here we present the first monolithic Yb:YAG DFB laser. The waveguide and the DFB structure were fabricated in the volume of an Yb:YAG crystal by ultrafast laser inscription. The DFB laser delivered 2 W of output power at a slope efficiency of 61% in SLM operation under pumping with an optically pumped semiconductor laser. This power level outperforms previously demonstrated dielectric DFB waveguide lasers by nearly an order of magnitude. Our approach paves the way for high power, compact, robust and highly efficient SLM laser sources.

Compact tunable photonic comb filter on silicon platform

Shuang Zheng, zhou nan, Yun Long, Zhengsen Ruan, Jing Du, Xiao Hu, Li Shen, Shuhui Li, and Jian Wang

Doc ID: 292700 Received 13 Apr 2017; Accepted 10 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: We propose and demonstrate a compact wavelength- and bandwidth-tunable photonic comb filter on silicon platform. It is a Fabry–Perot (FP) cavity fabricated on silicon-on-insulator, which is composed of two cascaded Sagnac-loop mirrors (SLMs) with multimode interferometer (MMI) assisted Mach-Zehnder interferometer (MZI) couplers. The effective length of the FP cavity and the reflectivity of SLMs can be dynamically changed based on thermal-optical effects by tuning three phase shifters along the cavity length and MZI arms, leading to center wavelength tuning and bandwidth tuning of the comb filter. Three tuning cases are investigated. By independently or simultaneously tuning three micro-heaters, the center wavelength tuning with a tuning efficiency of ~0.017 nm/mW and the bandwidth tuning from 4.37 to 27.6 GHz are achieved in the experiment.

Geometric phase morphology of Jones matrices

Dorilian Lopez-Mago, Arturo Canales, Raul Hernandez-Aranda, and Julio Gutierrez-Vega

Doc ID: 290965 Received 21 Mar 2017; Accepted 10 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: We demonstrate an innovative technique, based on the Pancharatnam-Berry phase, that can be used to determine whether an optical system characterized by a Jones matrix is homogeneous or inhomogeneous, containing orthogonal or nonorthogonal eigenpolarizations, respectively. Homogeneous systems have a symmetric geometric phase morphology showing line dislocations and sets of polarization states with equal geometric phase. In contrast, the morphology of inhomogeneous systems exhibits phase singularities, where the Pancharatnam-Berry phase is undetermined. The results show an alternative to extract polarization properties such as diattenuation and retardance and can be used to study the transformation of space-variant polarized beams.

Dependence of Atmospheric Refractive Index Structure Parameter (Cn2) on the Residence Time and Vertical Distribution of aerosols

Anand Sarma, S Satheesh, and Krishnamoorthy K

Doc ID: 292639 Received 18 Apr 2017; Accepted 10 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: Effects of absorbing atmospheric aerosols in modulating the tropospheric refractive index structure parameter (Cn2) are estimated using high resolution radiosonde and multi-satellite data along with a radiative transfer model. We report the influence of variations in residence time and vertical distribution of aerosols in modulating Cn2 and why the aerosol induced atmospheric heating need to be considered while estimating a Free Space Optical Communication link budget. The results show that performance of the link is seriously affected if large concentrations of absorbing aerosols reside for a long time in the atmospheric path.

Single-focus spiral zone plates

Yonghao Liang, Enliang Wang, Yilei Hua, Changqing Xie, and Tian-Chun Ye

Doc ID: 292923 Received 21 Apr 2017; Accepted 09 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: We extend the concept of spiral zone plates (SZPs) along the optical axis and define a specific single optical element, termed as single-focus spiral zone plates (SFSZPs), for the generation of single-focus vortex beam. The key idea is to make the transmittance of the SZPs sinusoidal in the azimuthal direction. Furthermore, a two-parameter modified sinusoidal apodization window is introduced to modulate the transmittance function. Theoretical analysis reveals that the third order diffraction light intensity of the SFSZPs could be reduced by more than three orders of magnitude as compared with a conventional SZP. The experimental results are also presented, confirming the desired single-focus characteristics. The unique single-focus phase singularity properties imply that SFSZPs may find a wide range of imaging and microscopy applications, as well as fundamental studies of vortex beams.

Mechanisms of surface contamination in fused silica by means of laser-induced electrostatic effect

Stavros Demos, Christopher Carr, and David Cross

Doc ID: 295170 Received 04 May 2017; Accepted 09 Jun 2017; Posted 13 Jun 2017  View: PDF

Abstract: We demonstrate that fused-silica samples exposed to nanosecond laser pulses at 355 nm and 1064 nm develop long-lived electrostatic charges on their surfaces. These charges extend well beyond the area exposed to the laser beam. The results suggest this effect is dependent on laser fluence and wavelength. In addition, ejected particles generated during laser-induced breakdown are electrostatically charged. Experiments indicate that such electrostatic charges can produce forces that can support the transport of dielectric and metallic microspheres between surfaces. This in turn can promote increased contamination of optical components during operation at relevant excitation conditions.

Wideband Tunable Opto-Electronic Oscillator based on Frequency Translation

Zeev Tamir, Asher Meltzer, and Moshe Horowitz

Doc ID: 290872 Received 25 Apr 2017; Accepted 09 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: We demonstrate a new method to obtain a widely tunable low phase-noise opto-electronic oscillator (OEO), based on translating the OEO signal into a lower intermediate frequency (IF) signal. The OEO signal is downconverted to IF by using an LO signal, filtered by a high-Q filter, and its frequency is then upconverted back into the high OEO frequency. The combination of a narrowband filter at a fixed central frequency with a tunable LO forms a tunable high-Q bandpass filter that can be used to change the OEO frequency over a broad frequency region. The effect of the LO phase noise on the OEO is suppressed by the dual frequency conversions. Hence, a tunable LO with a high phase noise can be used to control the frequency of an ultra-low phase noise OEO. The use of a bandpass filter with a lower center frequency than that of the OEO signal also enables increasing the effective Q-factor of the OEO filter.

Frequency-domain light intensity spectrum analyzer (f-LISA) based on temporal convolution

Chi Zhang, Liao Chen, duan hua, and Xinliang Zhang

Doc ID: 294965 Received 01 May 2017; Accepted 09 Jun 2017; Posted 16 Jun 2017  View: PDF

Abstract: We propose and experimentally demonstrate a new type of all-optical RF spectrum analyzer based on temporal convolution and cross-phase modulation (XPM), which can be regarded as the frequency-domain counterpart of conventional light intensity spectrum analyzer (LISA). The XPM effect converts the intensity envelope of an optical signal to the phase of the probe signal while the temporal convolution helps to enable the RF spectrum to be temporally resolved with high frame rate. This frequency-domain LISA (f-LISA) has experimentally demonstrated 800-GHz observation bandwidth (900 GHz in simulation) with 1.25-GHz resolution and 94-MHz frame rate. To showcase its potential applications, this analyzer has successfully characterized the dynamic RF spectrum of an ultrafast wavelength-switching signal with 10-ns switching interval. We believe that it is promising for some ultrafast dynamic RF spectrum acquisition applications, e.g. fast tuning lasers and real-time channel monitoring.

Effects of ambient air pressure on surface structures produced by ultrashort laser pulse irradiation.

Jijil JJ Nivas, Felice Gesuele, Elaheh Allahyari, Stefano Oscurato, Rosalba Fittipaldi, Antonio Vecchione, Riccardo Bruzzese, and Salvatore Amoruso

Doc ID: 296164 Received 18 May 2017; Accepted 08 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: We report an experimental analysis addressing striking effects of residual air ambient pressure, from atmospheric conditions (103 mbar) to high vacuum (10-4 mbar), on the surface structures induced on a silicon target by direct fs laser irradiation. We observe an interesting direct impact of the ambient pressure on the period and depth of the generated surface ripples as well as on the formation of surface micro-grooves. Moreover, a significant correlation is observed between the ripples period and depth. The change of pressure is accompanied by a variation of the degree of nanoparticles coverage on the irradiated surface, which is eventually recognized as an important factor for the development of the final surface structures. These results shed light on the intriguing mechanisms underlying the formation of the various surface textures generated by direct femtosecond laser surface structuring, also evidencing that the ambient pressure can act as an effective parameter to tailor some characteristic features of the processed surface.

Optoelectronic Oscillator incorporating Hollow Core Photonic Bandgap Fiber

Udara Mutugala, Joonyoung Kim, Tom Bradley, Natalie Wheeler, Seyed Reza Sandoghchi, John Hayes, Eric Rodrigue Numkam Fokoua, Francesco Poletti, Marco Petrovich, David Richardson, and Radan Slavik

Doc ID: 296550 Received 23 May 2017; Accepted 08 Jun 2017; Posted 08 Jun 2017  View: PDF

Abstract: We demonstrate the first Optoelectronic oscillator that uses Hollow-Core Photonic Bandgap Fiber (HC-PBGF) as a delay element of a sufficient length to allow for low-noise operation. We show experimentally that HC-PBGF can improve the temperature stability of the oscillator by a factor of more than 15 as compared to standard optical fiber. We also measured the oscillator’s phase noise, allowing evaluation of the suitability of HC-PBGF for this application. Additionally this work also provides the first characterization of the temperature stability of a long-length (>800 m in our study) of low-thermal sensitivity (2 ps/km/K) HC-PBGF wound on a spool.

Polymer micro-ring resonator integrated with a fiber ring laser for ultrasound detection

Heming Wei and Sridhar Krishnaswamy

Doc ID: 292811 Received 17 Apr 2017; Accepted 08 Jun 2017; Posted 09 Jun 2017  View: PDF

Abstract: Polymer micro-ring resonators fabricated by direct laser writing technique are presented as sensors for ultrasound detection. The optical micro-ring resonator consists of a micro-ring waveguide which acts as a wavelength selective feedback mirror to an erbium-doped fiber ring laser (EDFRL). The micro-ring resonator reflection spectrum determines the lasing frequencies of the FRL. Acoustic waves which cause strain or deformation of the micro-ring resonator lead to shifts of the resonance wavelength and thereby shifts in the FRL lasing spectrum. The spectral shifts are demodulated using an unbalanced Michelson interferometer. The experiments demonstrate that polymer micro-ring resonators integrated with a fiber ring laser can be used as adaptive high-frequency ultrasound detectors.

Fabrication of woodpile photonic structures through phase engineered interference lithography for omnidirectional optical filters

Saraswati Behera and Joby Joseph

Doc ID: 294982 Received 08 May 2017; Accepted 08 Jun 2017; Posted 09 Jun 2017  View: PDF

Abstract: In this paper, we report a large area and single step optical fabrication technique based on phase engineering interference lithography that is scalable and reconfigurable for the realization of submicrometer scale periodic face centered cubic (FCC) inverse woodpile photonic structures. The realized inverse woodpile structure on positive photoresist having 4 numbers of layers with 740 nm spatial and 1046 nm axial periodicities show 10% reflectance and 90% transmittance at 776 nm wavelength that can further be improved for more number of added axial layers. The realized structure can be transferred to crystalline silicon for realizing a band pass/rejection NIR filter in reflection/transmission mode. Further, woodpile structures based on low contrast silicon nitride (Si3N4) are designed as selective narrow frequency filters at 1310 nm and 1550 nm wavelengths for telecommunication applications and omnidirectional RGB filters for display devices by tuning the design parameters.

Static FT Imaging spectrometer based on SOI waveguide MZI array chip

Mingyu Li, Mingyue Yang, and Jian-Jun He

Doc ID: 291398 Received 28 Mar 2017; Accepted 08 Jun 2017; Posted 13 Jun 2017  View: PDF

Abstract: We proposed a large aperture push-broom static Fourier transform (FT) imaging spectrometer for hyper-spectral imaging. The spectroscopic system was based on the silicon-on-insulator (SOI) platform, consisting of spot size converters, Mach-Zehnder interferometer (MZI) array and a detector array. The arm length differences of the 201 MZI arrays are linearly varied. It is one on-chip FT spectrometer operating in a large spectral range from 1100 nm to 1700 nm with a resolution of 24 cm-1 and small foot print (Chip size: 1115 mm2). The waveguide MZI based large aperture push-broom FT spectrometer can provide a compact solution for high spectral resolution remote sensing in both the fore-optic lens and the spectroscopic system

Q-switching Yb3+:YAG lasers based on Plasmon Resonance Nonlinearities of Cu2−xSe@Cu2−xS nanorods

Yi Zhan, Yimeng Wang, Jinlin Long, jifeng ZU, Li Wang, Congcong Wang, Ting Qu, and Qian Liu

Doc ID: 296078 Received 19 May 2017; Accepted 07 Jun 2017; Posted 09 Jun 2017  View: PDF

Abstract: Copper(II) chalcogenide nanocrystals, including Cu2−xY (Y = S, Se, and Te), have an intense localized surface plasmon resonance (LSPR) band in the near-infrared (NIR) region. In this research, colloidal Cu2−xSe@Cu2-xS nanorods were synthesized using the organometallic colloidal and cation-exchange methods. The dynamics of LSPR were investigated using ultrafast laser pulses via pump–probe experiments in the NIR region. Investigation of the transient absorption spectra revealed an LSPR spectral band from approximately 850 to 1350 nm, with a center wavelength of 1030 nm. The kinetics of the recovering plasmon maximum, probed at the peak wavelength of 1030 nm, exhibited a strong nonlinear response for plasmonic absorption, with a modulation depth exceeding 25% in the transmitted signal under a pump fluence of 3.97 mJ/cm2. The ultrafast nonlinear optical properties of these plasmonic nanoparticles could be used as excellent saturable absorbers (SAs) in ultrafast lasers. A compact passively Q-switched Yb3+:YAG microchip laser with a Cu2−xSe/Cu2 − xS SA was investigated. Furthermore, a maximum average output power of 187 mW was obtained, with a pulse energy of 4.11 μJ, pulse duration of 8.5 μs, and repetition rate of 45.45 kHz at a pump power of 8.7 W.

Self-Frequency-Doubling in a Laser-Active Whispering-Gallery Resonator

Simon Herr, Yannick Folwill, Karsten Buse, and Ingo Breunig

Doc ID: 297013 Received 29 May 2017; Accepted 07 Jun 2017; Posted 09 Jun 2017  View: PDF

Abstract: Lasing and self-frequency-doubling are achieved in a mm-sized laser-active whispering-gallery resonator made of neodymium-doped lithium niobate. A low-cost 808-nm laser diode without external frequency stabilization is sufficient to pump the neodymium ions.Laser oscillation around 1.08 µm drives a frequency-doubling process within the same cavity providing green light. The electrical-optical efficiency of the system reaches up to 2 x 10^{-4}.To the best of our knowledge, this is the first demonstration of combining lasing and χ (²) frequency conversion in a single high-Q whispering-gallery resonator. This approach is general and can be applied to other materials and other nonlinear optical processes.

Cross-polarized, multi-octave supercontinuum generation

Haochuan Wang, Ayman Alismail, Gaia Barbiero, maximilian Wendl, and Hanieh Fattahi

Doc ID: 294944 Received 05 May 2017; Accepted 07 Jun 2017; Posted 08 Jun 2017  View: PDF

Abstract: Generation of superoctave spectra from the interaction of intense ultrashort optical pulses and cubic non-linearity is the result of an interplay between the dispersion and nonlinearity of a material and various propagation effects. The cubic nonlinearity can be enhanced when it is combined with a quadratic cascaded nonlinearity, relaxing the requirement on the laser’s peak intensity for supercontinuum (SC) generation. In this paper, we demonstrate and compare generation of a SC driven from cubic and cascadedquadratic nonlinearities at anomalous and zero dispersion wavelength (ZDW). We show, filament-free SC generation of femtosecond mid-infrared pulses by harvesting cascaded quadratic nonlinearity and at ZDW requires a lower threshold peak intensity and results in a higher power spectral density for the newly generated spectral components. The presented method is a suitable approach for generating multi-octave spectra from low peak-power, high average-power oscillators or a suitable seed for optical parametric amplifiers and multi-octave field synthesizers.

Raman tailored photonic-crystal-fiber for telecom band photon-pair generation

Martin Cordier, Adeline Orieux, Renaud Gabet, Thibault HARLÉ, Nicolas Dubeuil, Eleni Diamanti, Philippe Delaye, and Isabelle Zaquine

Doc ID: 295939 Received 19 May 2017; Accepted 07 Jun 2017; Posted 08 Jun 2017  View: PDF

Abstract: We report on the experimental characterization of a novel nonlinear liquid-filled hollow-core photonic-crystal fiber for the generation of photon pairs at telecommunication wavelength through spontaneous four-wave-mixing. We show that the optimization procedure in view of this application links the choice of the nonlinear liquid to the design parameters of the fiber, and we give an example of such an optimization at telecom wavelengths. Combining the modeling of the fiber and classical characterization techniques at these wavelengths, we identify, for the chosen fiber and liquid combination, spontaneous four-wave-mixing phase matching frequency ranges with no Raman scattering noise contamination. This is a first step toward obtaining a telecom band fibered photon-pair source with ahigh signal-to-noise ratio

Adaptive aberration correction of a 5J/6.6ns/200Hz solid-state Nd:YAG laser

xin yu, Lizhi Dong, boheng lai, ping yang, Wenjin Liu, Shuai Wang, Guomao Tang, JiSi Qiu, Zhijun Kang, Yong Liu, Bing Xu, Shanqiu Chen, Hau Liu, and Yueliang Liu

Doc ID: 294614 Received 10 May 2017; Accepted 07 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: In this work, we present an adaptive aberration correction system to simultaneously compensate for aberrations and reshaping the beams. A low-order aberration corrector is adapted. In this corrector, four lenses are mounted on a motorized rail, whose positions can be obtained using ray tracing method based on the beam parameters detected by a wave-front sensor. After automatic correction, the PV value of the wave-front is reduced from 26.47μm to 1.91μm and the beam quality β is improved from 18.42 to 2.86 times of diffraction limit. After further correction with a deformable mirror, the PV value of the wave-front is less than 0.45μm and beam quality is 1.64 times of diffraction limit. To the best of our knowledge, this is the highest performance from such a high power, high pulse repetition rates Nd: YAG solid state laser ever built.

An approach for multiplexing fiber communication with cylindrical vector beams

Xiaocong Yuan, Ting Lei, Wen Qiao, She Gao, Z Li, and Zhentian Wu

Doc ID: 295672 Received 09 May 2017; Accepted 06 Jun 2017; Posted 06 Jun 2017  View: PDF

Abstract: Cylindrical vector beams (CVBs) including radial, azimuthal and hybrid polarization vortex states, are based on the polarization singularity and regarded as the eigen modes of fiber. In this paper, we propose and demonstrate CVBs (de)multiplexing communication in a few-mode fiber (FMF). We simulate the 8 CVB modes including ±1 order and ±2 order supported by the FMF. We measure the modes purity of ±1 order and ±2 order CVBs which can reach 67.87%, 69.26%, 73.84% and 71.95% after transmission in the 5 km FMF. The mode crosstalk between the CVBs and their adjacent orders is less than -7.54dB. In the experiment, we demonstrate 4 modes of coaxial CVBs multiplexing communication with the orders of ±2 and spatially orthogonal polarization states. Each CVB modes carrying 10Gbit/s on-off keying signals are transmitted in 5 km FMF, and achieve bit-error rate below the forward error correction threshold of 3.8×10-3.

Room-temperature, rapidly-tunable, green-pumped continuous-wave optical parametric oscillator

Kavita Devi and Majid Ebrahim-Zadeh

Doc ID: 294861 Received 28 Apr 2017; Accepted 06 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: We report the first realization of a high-power, single-frequency, green-pumped continuous-wave optical parametric oscillator (OPO) capable of providing rapid and continuous tuning across wide spectral range in the near-infrared at room temperature. By exploiting the nonlinear crystal of MgO:sPPLT in a fan-out grating design, pumped at 532 nm in the green, the OPO can be tuned continuously across 1097–2100 nm in the idler, with corresponding signal tuning over 712–1033 nm using simple mechanical translation of the crystal at fixed temperature. The device can deliver hundreds of mW of idler power across the complete tuning range, with as much as 2.2 W at 1097 nm for 9 W of input pump power at 77% pump depletion. The passive power stability of the generated idler at 1110 nm, measured at 6.8 W of pump power, is better than 1% rms over 30 minutes. The signal frequency stability, measured at 837 nm, is 518 MHz over 2 minutes, with an instantaneous linewidth of 6.9 MHz, in high beam quality.

Second Harmonic Generation in Single CdSe Nanowires by Focused Cylindrical Vector Beams

Xiao Wang, Zhouxiaosong Zeng, Xiujuan Zhuang, Frank Wackenhut, anlian pan, and Alfred Meixner

Doc ID: 296058 Received 15 May 2017; Accepted 05 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: Cylindrical vector beams with radial or azimuthal polarization have created great interest due to their unique focusing characteristics and focal components. In this work, we investigate second-harmonic general (SHG), of single CdSe nanowires (NWs) excited by tightly focused cylindrical vector beams of 150 fs pulses at 800 nm. With the specific polarizations in the focal region, we demonstrate a three-dimensional interaction between the focal electric field components and the NWs. The excitation anisotropy of the SHG can directly be derived from the imaging patterns with the cylindrical vector beams. The highest SHG excitation efficiency is observed when the polarization is parallel to the long axis of the NW, which is confirmed by the conventional linear polarization approach. Our work with cylindrical vector beams provides a new approach to study the nonlinear phenomenon of single semiconductor NWs in three dimensions and it could be applied to many other nanoscale systems.

Right- and Left-Handed Rules on the Transverse Spin Angular Momentum of Surface Wave of Photonic Crystal

bing hu, Xia feitong, Xiaoshu Cai, shengnan tian, Hanming Guo, and Songlin Zhuang

Doc ID: 295860 Received 12 May 2017; Accepted 05 Jun 2017; Posted 06 Jun 2017  View: PDF

Abstract: By investigating the surface wave of photonic crystal (PhC) we put forward two sets of rule: the right-handed screw rule, determining the transverse spin angular momentum (SAM) directions according to the propagation direction of surface wave; the left-handed rule, determining the excitation direction of surface wave in terms of the SAM direction of incident circularly polarized light (CPL) and the relative position of dipole-like scatterer with respect to the interface where surface wave propagates. Both right- and left-handed rules apply to the interface consisting of opposite-sign-permittivity materials. With the help of these two sets of rule it is convenient to determine the direction of transverse SAM and of excited surface wave, which facilitate the applications involving transverse SAM of surface wave.

Growth and lasing performance of a Tm,Y:CaF₂ crystal

Xinyang Liu, Shengzhi Zhao, Tao Li, Kejian Yang, Chao Luan, xinsheng guo, Beibei Zhao, Lihe Zheng, Liangbi Su, Jun Xu, and Jintian Bian

Doc ID: 295224 Received 08 May 2017; Accepted 05 Jun 2017; Posted 06 Jun 2017  View: PDF

Abstract: A novel Tm3+ ion and Y3+ ion co-doped CaF₂ crystal was grown and characterized, which spectral and lasing performance were presented for the first time, to the best of our knowledge. Under diode-end-pumping, in continuous-wave (CW) regime, maximum output power of 453 mW was delivered under an absorption pump power of 2.5 W, corresponding to an optical-optical conversion efficiency of 17.9% and a slope efficiency of 21%. With a birefringent quartz plate, wavelength tunable operation with a tunable range of more than 190 nm was realized. The results show that Tm,Y:CaF₂ is a promising laser crystal operating at 2 μm region. © 2017 Optical Society of America© 2017 Optical Society of America

Optical Correlation-based Cross-domain Image Retrieval System

Kanami Ikeda, Hidenori Suzuki, and Eriko Watanabe

Doc ID: 293158 Received 26 Apr 2017; Accepted 05 Jun 2017; Posted 06 Jun 2017  View: PDF

Abstract: A novel cross-domain image retrieval system that is based on a high-speed optical correlator with a coaxial holographic system is presented. Our newly designed conversion module allows various kind of data to be converted to pagedata with a uniform optical intensity for the optical correlator using an autoencoder, which has been difficult with any other conventional methods. We performed experiments to demonstrate the utility of the system with our conversion module and optical correlator. A sketch-based cross-domain image retrieval system with the goal of discovering similar photos by querying freehand human sketches was demonstrated. The optical correlation-based system can be utilized in conventional models for research on deep learning, and further applications are expected in the future.

Two-color field enhancement at an STM junction for spatiotemporally-resolved photoemission

Xiang Meng, Wencan Jin, Hao Yang, Jerry Dadap, Richard Osgood, Andrei Dolocan, Peter Sutter, and Nicholas Camillone III

Doc ID: 292273 Received 19 Apr 2017; Accepted 04 Jun 2017; Posted 05 Jun 2017  View: PDF

Abstract: We report measurements and numerical simulations of ultrafast laser-excited carrier flow across a scanning tunneling microscope (STM) junction. The spatiotemporally-resolved current from a nanoscopic tungsten tip across a ~1-nm vacuum gap to a silver surface is driven by a two-color excitation scheme that uses an optical delay-modulation technique to extract the two-color signal from background contributions. The role of optical field enhancements at the junction in driving the current is investigated using density functional theory (DFT) and full 3D finite-difference time-domain (FDTD) computations. We find that simulated field-enhanced two-photon photoemission (2PPE) currents are in excellent agreement with the observed exponential decay of the two-color photoexcited current with increasing tip–surface separation, as well as the optical-delay dependence of the current. The results suggest an approach to 2PPE with simultaneous subpicosecond temporal and nanometer spatial resolution.

THz pulse generation from (111)-cut InSb and InAs crystals when illuminated by 1.55-µm femtosecond laser pulses

Ignas Nevinskas, Kristijoas Vizbaras, Augustinas Trinkūnas, Renata Butkutė, and Arunas Krotkus

Doc ID: 296074 Received 16 May 2017; Accepted 02 Jun 2017; Posted 08 Jun 2017  View: PDF

Abstract: Terahertz pulse generation from p-InAs, p-InSb and n-InSb epitaxial layers are investigated using 1.55-µm wavelength femtosecond laser pulses for photoexcitation. The samples are of (111) crystallographic orientation resulting in anisotropic photoconductivity. Experiments have shown that terahertz generation in InAs is mainly due to anisotropic photocurrent in the surface electric field while a dominant mechanism in InSb is optical rectification. At high optical excitation fluencies, InSb is more efficient than p-InAs. In the presence of external magnetic field, (111) InSb has exhibited promising viability as an alternative to the photoconductive antenna emitter in a THz-TDS system.

Polarization-maintaining, large effective-area higher order modes fiber

Raja Ahmad, Man Yan, Jeffrey Nicholson, Kazi Abedin, Paul Westbrook, Clifford Headley, p wisk, Eric Monberg, and David DiGiovanni

Doc ID: 292523 Received 13 Apr 2017; Accepted 01 Jun 2017; Posted 05 Jun 2017  View: PDF

Abstract: Higher-order-mode (HOM) fibers guiding light in large effective-area (Aeff) Bessel-like modes have recently generated great interest for high-power laser-applications. A polarization-maintaining (PM) version of HOM fibers can afford the added possibility of coherent-beam combination, improved material processing, and polarization multiplexing of high-power fiber-lasers. We report a PM-HOM fiber for guiding Bessel-like modes with A_{eff} ranging from 1200-2800 µm^{2}. The fiber-modes exhibit a birefringence value that compares well with that of a conventional single-mode PM-fiber (2×10^{- 4}), and exhibit a polarization-extinction-ratio ranging from 13- dB over meter-long fiber lengths, practical for amplifier systems. This fiber presents a unique platform for next-generation high-power fiber-systems, as well as for the fundamental studies on deterministically-polarized Bessel-like modes in fibers.

Critical dimension metrology of a plasmonic photonic crystal based on Mueller matrix ellipsometry and the reduced Rayleigh equation

Jean-Philippe Banon, Torstein Nesse, Zahra Ghadyani, Morten Kildemo, and Ingve Simonsen

Doc ID: 295878 Received 12 May 2017; Accepted 31 May 2017; Posted 31 May 2017  View: PDF

Abstract: A computationally efficient algorithm based on the reduced Rayleigh equation, combined with an optimization scheme, is used to accurately retrieve the morphological parameters of a two-dimensional plasmonic photonic crystal from angle-resolved spectroscopic Mueller matrix ellipsometric measurements. The numerical method is successfully tested against experimental data and gives morphological parameters consistent with SEM and AFM measurements.

Elliptical mirror-based TIRF microscopy with shadowless illumination and adjustable penetration depth

Jian Liu, Qiang Li, Mengzhou Li, Shan Gao, Chenguang Liu, Limin Zou, and Jiubin Tan

Doc ID: 295783 Received 11 May 2017; Accepted 31 May 2017; Posted 08 Jun 2017  View: PDF

Abstract: We propose an elliptical mirror-based TIRF (e-TIRF) microscopy with shadowless illumination and adjustable penetration depth. The elliptical mirror is used to produce a hollow cone illumination with all azimuthal directions and a large range of incident angle, so as to attenuate the potential shadow effects when utilizing a single direction illumination, such as asymmetries and low contrast. The experiment demonstrates that e-TIRF method can realize shadowless imaging with symmetric intensity distribution. Meanwhile, the penetration depth of e-TIRF can be theoretically adjusted from 58 nm to 250 nm by adjusting the size of aperture or the position of an opaque mask. This method extends the minimum penetration depth, which is useful for high axial resolution.

Experimental validation of phase-only pre-compensation over 494 m free-space propagation

Aoife Brady, René Berlich, Nina Leonhard, Teresa Kopf, Paul Böttner, Ramona Eberhardt, and Claudia Reinlein

Doc ID: 291814 Received 04 Apr 2017; Accepted 30 May 2017; Posted 12 Jun 2017  View: PDF

Abstract: It is anticipated that ground-to-GEO laser communication will benefit from pre-compensation of atmospheric turbulence for laser beam propagation through the atmosphere. Theoretical simulations and laboratory experiments have determined its feasibility, extensive free space experimental validation has however yet to be fulfilled. Therefore, we designed and implemented an Adaptive Optical (AO-) Box which pre-compensates an outgoing laser beam (uplink) using measurements of an incoming beam (downlink). The setup was designed to approximate the baseline scenario over a horizontal test range of 0.5km and consisted of a ground terminal with the AO-Box and a simplified approximation of a satellite terminal. Our results confirmed that we could focus the uplink beam on the satellite terminal using AO %based on measurements of the downlink wavefront, under a point-ahead-angle of 28 µrad. Furthermore, we demonstrated a considerable increase in intensity received at the satellite. These results are further testimony to AO pre-compensation being a viable technique to enhance Earth-to-GEO optical communication.

Unidirectional waveguide grating antennas with uniform emission for optical phased arrays

Manan Raval, Christopher Poulton, and Michael Watts

Doc ID: 294606 Received 26 Apr 2017; Accepted 29 May 2017; Posted 06 Jun 2017  View: PDF

Abstract: We demonstrate millimeter-scale optical waveguide grating antennas with unidirectional emission for integrated optical phased arrays. Unidirectional emission eliminates the fundamental problem of blind spots in the element factor of a phased array caused by reflections of antenna radiation within the substrate. Over 90% directionality is demonstrated using a design consisting of two silicon nitride layers. Furthermore, the perturbation strength along the antenna is apodized to achieve uniform emission for the first time on a millimeter scale. This allows for a high effective aperture and receiving efficiency. The emission profile of the measured 3mm long antenna has a standard deviation of 8.65% of the mean. These antennas are state of the art and will allow for integrated optical phased arrays with blind-spot-free high transmission output power and high receiving efficiency for LIDAR and free-space communication systems.

Depth-layer weighted prediction method for full-color polygon-based holographic system with real objects

Yu Zhao, Ki-Chul Kwon, Yan-Ling Piao, Jeon Seok, and Nam Kim

Doc ID: 292730 Received 14 Apr 2017; Accepted 28 May 2017; Posted 02 Jun 2017  View: PDF

Abstract: We propose a full-color polygon-based holographic system for real three-dimensional (3-D) objects using a depth-layer weighted prediction method. The proposed system is comprised of four main stages: acquisition, preprocessing, hologram-generation, and reconstruction. In the preprocessing stage, the point cloud model is separated into red, green, and blue (RGB) channels with depth-layer weighted prediction. We characterize the color component values based on the depth information of the real object. Then the color prediction was derived from the measurement data. The computer-generated holograms (CGHs) reconstruct 3D full-color images with a deep sensation of depth caused by polygon approach. The feasibility of the proposed method is confirmed by numerical and optical reconstruction.

Low photon count based digital holography for quadratic phase cryptography

Inbarasan Muniraj, Changliang Guo, Ra'ed Malallah, James Ryle, John Healy, Byung-Geun Lee, and John Sheridan

Doc ID: 292072 Received 05 Apr 2017; Accepted 28 May 2017; Posted 16 Jun 2017  View: PDF

Abstract: Recently, the vulnerability of the linear canonical transform (LCT) based double random phase encryption (DRPE) system to attack has been demonstrated. To alleviate this, we present, for the first time, a method for securing a 2D scene using a quadratic phase encoding system (QPES) operating in the photon counted imaging (PCI) regime. Position-phase-shifting digital holography (PPSDH) is applied to record the photon-limited encrypted complex samples. The reconstruction of the complex wave front involves four sparse (under- sampled) dataset intensity measurements (interferograms) at two different positions. Computer simulations validate that the photon-limited sparse-encrypted data has adequate information to authenticate the original data set. Finally, security analysis, employing iterative phase retrieval attacks, has been performed.

The impact of curvature on the optimal configuration of flexible luminescent solar concentrators

Mark Portnoi, Christian Sol, Clemens Tummeltshammer, and Ioannis Papakonstantinou

Doc ID: 290975 Received 21 Mar 2017; Accepted 26 May 2017; Posted 05 Jun 2017  View: PDF

Abstract: Flexible Luminescent Solar Concentrators (LSCs) could deliver integrated photovoltaics in all aspects of our lives, from architecture to wearable electronics. We present and experimentally verify a model for the op- timization of the external optical efficiency of LSCs under varying degrees of curvature. We demonstrate differences between the optimization of flat and bent LSCs, showing that optimal fluorophore concentrations can differ by a factor of two.

High resolution monochromator using high efficiency single-mode x-ray resonator at Laue incidence

Yu-Hsin Wu, Yi-Wei Tsai, Wen-Chung Liu, Yu-Chieh Chih, and Shih-Lin Chang

Doc ID: 291407 Received 30 Mar 2017; Accepted 26 May 2017; Posted 05 Jun 2017  View: PDF

Abstract: We report a high resolution and efficiency monochromator with energy resolution, ΔE/E~2.08*10^(-7), utilizing a hard x-ray single-mode Fabry-Perot (FP) resonator at Laue incidence at 14.4388 keV. Instead of using multiple-crystal diffraction via several asymmetric-cut crystals, a 3 meV single-peak is generated from the interference of a Si-made 2-plate cavity with a thickness of 70 μm and a gap of 45 μm, where a (0 -4 0) Laue reflection is used to excite the back reflection (12 4 0) for the enhancement of the FP efficiency. Due to the large angular acceptance of (12 4 0) and (0 -4 0), the energy tunability can be achieved by changing the incident angle into the resonator. The application of x-ray resonators at Laue incidence as monochromator can be further implemented to x-ray optics.

Low Loss Kagome Hollow-Core Fibers Operating from the Near- to the Mid-IR

Natalie Wheeler, Thomas Bradley, John Hayes, Marcelo Gouveia, Sijing Liang, Yong Chen, Seyed Reza Sandoghchi, Seyed Mohammad Abokhamis Mousavi, Francesco Poletti, Marco Petrovich, and David Richardson

Doc ID: 285820 Received 31 Jan 2017; Accepted 28 Apr 2017; Posted 04 May 2017  View: PDF

Abstract: We report the fabrication and characterization of Kagome hollow core antiresonant fibers with reduced attenuation, low bend loss and high modal purity. Record low attenuation values are reported: 12.3 dB/km, 13.9 dB/km and 9.6 dB/km in three different fibers optimized for operation at 1 µm, 1.55 µm and 2.5 µm respectively. These fibers are excellent candidates for ultrahigh power delivery at key laser wavelengths including 1.064 µm and 2.94 µm, as well as for applications in gas-based sensing and non-linear optics.

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