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Accepted papers to appear in an upcoming issue

OSA now posts prepublication articles as soon as they are accepted and cleared for production. See the FAQ for additional information.

Exciting Surface Waves on Metal-Coated Multimode Optical Waveguides using Skew Rays

Han Chunyang, John Canning, Kevin Cook, Md. Arafat Hossain, and Hui Ding

Doc ID: 274884 Received 31 Aug 2016; Accepted 25 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: Multi-point SPR excitation using a skew ray within a multimode plastic optical waveguide coated with gold, Au, is reported. The effect of skew rays on the performance of SPR has been studied both theoretically and experimentally. The approach also entails a novel method of measuring the SPR angle which is in agreement with theoretically predicted values.

Low-frequency Raman spectroscopy using atomic filters

Xiaobo Xue, Zhiwen Liu, Corey Janisch, Yizhu Chen, and Jingbiao Chen

Doc ID: 276458 Received 27 Sep 2016; Accepted 25 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: A Faraday anomalous dispersion optical filter (FADOF) and an atomic resonant absorption filter are used in tandem to demonstrate low-frequency Raman measurement down to few cm¯¹. The FADOF, with an ultralow bandwidth of 0.08 cm¯¹ at 780 nm, serves as a band-pass filter while the rubidium atomic cell acts as a notch filter, which has a bandwidth of 0.3 cm¯¹. Proof-of-concept study to measure Raman signal generated from silica optical fiber is performed, demonstrating low-frequency measurement of both the Stokes and the anti-Stokes shift down to 3 cm¯¹ at an equivalent signal level. These results indicate the prospect for GHz-THz Raman spectroscopy based on atomic filters.

Experimental Demonstration of Phase-Sensitive Regeneration of a BPSK Channel without Phase-Locked Loop using Brillouin Amplification

Ahmed Almaiman, Yinwen Cao, Morteza Ziyadi, Amirhossein Mohajerin Ariaei, Peicheng Liao, Changjing Bao, FATEMEH ALISHAHI, Ahmad Fallahpour, Bishara Shamee, Nisar Ahmed, Asher Willner, Youichi Akasaka, Tadashi Ikeuchi, Shigehiro Takasaka, Ryuichi Sugizaki, Steven Wilkinson, Joseph Touch, Moshe Tur, and Alan Willner

Doc ID: 275937 Received 14 Sep 2016; Accepted 23 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: All-optical phase regeneration of a BPSK signal is demonstrated at 10-30 Gb/s without a phase-locked loop in a PSA-based system using Brillouin amplification of the idler. The system achieves phase noise reduction of up to 56% and up to 11 dB OSNR gain at 10-5 BER for the 10 Gb/s signal. The system’s sensitivity to different parameters and stability is also evaluated.

Understanding the vibrational mode specific polarization effects in femtosecond Raman-induced Kerr-effect spectroscopy

Richard Van Duyne, Michael McAnally, Yinsheng Guo, Gurusamy Balakrishnan, and George Schatz

Doc ID: 275596 Received 09 Sep 2016; Accepted 23 Oct 2016; Posted 24 Oct 2016  View: PDF

Abstract: Optically heterodyne detected femtosecond Raman-induced Kerr-effect spectroscopy (OHD-FRIKES) was observed in neat cyclohexane. In the present study, an examination of the effect of the Raman pump ellipticity on the multiplex OHD-FRIKES spectra is discussed. The Raman pump ellipticity scanned OHD-FRIKES results reproduce anomalous observables from previous OHD-FRIKES experiments, and suggest new methods of tracking transient vibrational mode polarization in complex systems.

Dual-mode waveguide crossing utilizing taper assisted multimode-interference couplers

Yaocheng Shi and Hongnan Xu

Doc ID: 272151 Received 22 Jul 2016; Accepted 22 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: A dual-mode waveguide crossing is proposed and realized for the application of on-chip multimode interconnection. The present structure is achieved by two 90° crossed multimode-interference (MMI) couplers connected by four tapers. By properly choosing the width and length of the MMI section, the self-images for the incident TM0 mode and TM1 mode could be both at the center of the crossing. The characterization results for the fabricated device show that low insertion loss below ~1.5 dB and low crosstalk below ~−18 dB can be achieved over a large bandwidth more than 80 nm for both TM0 and TM1 modes.

Low-Power Electro-Optic Digital-to-Analog Converter using Cascaded Microring Modulator

Raphaël Dubé-Demers, Wei Shi, and Sophie LaRochelle

Doc ID: 274683 Received 31 Aug 2016; Accepted 22 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: Future super-computer interconnect systems and data centers request ultrahigh data rate links at low cost and power consumption, for which transmitters with high-level of integration and spectral efficient formats are key components. We report 60 Gb/s pulse-amplitude modulation (PAM-4) of an optical signal using a dual-microring silicon photonics circuit, making a low power, on-chip, electro-optic digital-to-analog converter (DAC), and modulator. The power consumption is evaluated below 100 fJ/bit, including thermal adjustments. To the best of our knowledge, these results feature the lowest reported power consumption for PAM signaling in a DAC-less scheme for data rate beyond 40 Gb/s.

Resonant Nanopillars arrays for label-free Biosensing

Miguel Holgado, Ana Hernandez, Rafael Casquel, Iñaki Cornago, Fátima Fernández, Paula Ciaurriz, Beatriz Santamaría, Francisco Javier Sanza, María Victoria Maigler, and María Fé Laguna

Doc ID: 267879 Received 08 Jun 2016; Accepted 21 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: In our previous work we demonstrated for the first time the experimental capability of Resonant Nanopillars arrays (R-NP) as biochemical transducers. In this work, we have evidenced the capability and suitability of R-NP arrays on a chip to function as label-free optical multiplexed biosensors. R-NP are based on Si3N4/SiO2 Bragg Reflectors with a cavity of SiO2. In order to demonstrate the biosensing performance, R-NP were biofunctionalized by the immobilization of IgG antibodies acting as bioreceptor. This immobilization was carried out through the silanization of pillars sensing surface with APTMS. R-NP were integrated in 8 different sensing arrays on a quartz surface chip. An optical fiber bundle monitored each sensing array vertically and independently after each biofunctionalization step, and subsequently after every recognition event of increasing concentrations of anti-IgGs. The results report a novel multiplexed optical biosensor made of 8 sensing arrays on a chip with promising performance and yield.

Experimental demonstration of compact spoof localized surface plasmons

Di Bao, Khalid Rajab, Wei Xiang Jiang, Qiang Cheng, Zhen Liao, and Tie Jun Cui

Doc ID: 276281 Received 23 Sep 2016; Accepted 21 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: In recent years, the study of generating and detecting localized surface plasmons (LSPs) has been expanded from the optical regime to microwave regime. In this work, the compact spoof LSPs are introduced through both numerical simulations and near-field measurements. It is observed that the compact LSP structure could effectively reduce the resonant frequency with stronger resonance strength (Gdbsm) and higher Q factor. Both electric near-field and surface-current distributions are monitored to examine the resonance processes of the LSP particle.

Optical path squeezing interferometry: boosting the resolution for Fourier transform imaging spectrometers

Jianxin Li, Caixun Bai, Yan Shen, and Donglei Xu

Doc ID: 275759 Received 12 Sep 2016; Accepted 21 Oct 2016; Posted 21 Oct 2016  View: PDF

Abstract: We present an optical path squeezing interferometer dedicated to high spectral resolution Fourier transform imaging spectrometry. By incorporating a pair of gratings into a Sagnac interferometer, the short-wavelength light has a larger optical path difference (OPD) than the long-wavelength light. The interference fringes with different OPD are squeezed into the same sampling window in data acquisition. As a result, the spectral resolution is greatly enhanced without large OPD scanning. Experimental results demonstrate that the proposed method is a promising technology for high-resolution spectral imaging.

Monolithically Integrated Reconfigurable Add-Drop Multiplexer for Mode-Division-Multiplexing Systems

Daoxin Dai, Wang Shipeng, Hon Tsang, and hao wu

Doc ID: 277552 Received 26 Sep 2016; Accepted 21 Oct 2016; Posted 21 Oct 2016  View: PDF

Abstract: An integrated reconfigurable optical add-drop multiplexer (ROADM) for mode-division-multiplexing (MDM) systems is proposed and demonstrated for the first time. We present a ROADM with four mode-channels, comprising a four-channel mode demultiplexer, four identical 2×2 thermo-optic Mach-Zehnder switches (MZS) and a four-channel mode multiplexer, which are integrated monolithically on silicon. All the devices were designed for operation with the quasi-TM polarization mode of the waveguides. The ROADM can add or drop any one of the mode channels individually by thermally turning on or off the corresponding MZS. The ROADM for MDM systems was fabricated on a silicon-on-insulator (SOI) wafer and had a footprint of 1.9mm × 1.0mm.

Transition from capacitive coupling to direct charge transfer in asymmetric terahertz plasmonic assemblies

Arash Ahmadivand, Raju Sinha, BURAK GERISLIOGLU, Mustafa Karabiyik, Nezih Pala, and Michael Shur

Doc ID: 278457 Received 10 Oct 2016; Accepted 21 Oct 2016; Posted 21 Oct 2016  View: PDF

Abstract: We numerically and experimentally analyze the charge transfer THz plasmons using asymmetric plasmonic assembly of metallic V-shaped blocks. The asymmetric design of the blocks allows for the excitation of classical dipolar and multipolar modes due to the capacitive coupling. Introducing a conductive microdisk between the blocks we facilitated the excitation of the charge transfer plasmons and studied their characteristics along with the capacitive coupling by varying the size of the disk.

Enhanced sensitivity in single-mode Si3N4 stadium resonators at visible wavelengths

Mario Chemnitz, Gabriele Schmidl, Anka Schwuchow, Matthias Zeisberger, Uwe Hubner, Karina Weber, and Markus Schmidt

Doc ID: 274838 Received 05 Sep 2016; Accepted 21 Oct 2016; Posted 21 Oct 2016  View: PDF

Abstract: Marker-free and non-invasive detection of analyte traces in aqueous solution using integrated optical resonators is an emerging technique within bioanalytics. Here, we present a single-mode silicon-nitride stadium resonator operating at the red edge of the visible spectrum, showing sensitivities larger than 200 nm/RIU and transmission dips with extinction ratios up to 15 dB. We present a mathematical model that allows optimization of the resonator sensitivity using the mode properties only, revealing that optimal sensing conditions are achieved for TM-polarized modes close to modal cut-off. The short operation wavelength makes the system especially suitable for nanoparticle enhanced sensing potentially down to the single-molecule limit.

Three Photon Absorption in Optical Parametric Oscillators Based on OP-GaAs

Oliver Heckl, Bryce Bjork, Georg Winkler, P. Bryan Changala, Benjamin Spaun, Gil Porat, Thinh Bui, Kevin Lee, Jie Jiang, Martin Fermann, Peter Schunemann, and Jun Ye

Doc ID: 275159 Received 02 Sep 2016; Accepted 20 Oct 2016; Posted 21 Oct 2016  View: PDF

Abstract: We report on the first singly-resonant (SR), synchronously pumped optical parametric oscillator (OPO) based on orientation-patterned gallium arsenide (OP-GaAs). Together with a doubly resonant (DR) degenerate OPO based on the same OP-GaAs material, the output spectra cover 3 to 6 µm within ~3 dB of relative power. The DR-OPO has the highest output power reported to date from a femtosecond, synchronously pumped OPO based on OP-GaAs. We discovered strong three photon absorption with a coefficient of 0.35 ± 0.06 cm3/GW2 for our OP-GaAs sample, which limits the output power of these OPOs as mid-IR light sources. We present a detailed study of the three photon loss on the performance of both the SR and DR-OPOs, and compare them to those without this loss mechanism.

Efficient sub-joule energy extraction from a diode-pumped Nd:LuAG amplifier seeded by a Nd:YAG laser

Xing Fu, Qiang Liu, Mali Gong, Tinghao Liu, and Zhan Sui

Doc ID: 275544 Received 13 Sep 2016; Accepted 20 Oct 2016; Posted 21 Oct 2016  View: PDF

Abstract: We report a joule-level diode-pumped Nd:YAG-Nd:LuAG hybrid active mirror amplifier chain (HAMAC), producing an output energy of 1.52 J at 10 Hz in a 10 ns Q-switched pulse, while a pulse energy of 6 mJ is extracted from the Nd:LuAG stage, corresponding to an optical-to-optical efficiency of 21.7%. To our knowledge, this is the first demonstration of high energy nanosecond pulse amplification in a Nd:LuAG laser with extracted pulse energies approaching the joule level. The excellent scaling performance confirms Nd:LuAG as a very promising gain medium for high-energy, short-pulse lasers.

High-efficiency WSi superconducting nanowire single-photon detectors for quantum state engineering in the near infrared

Julien LAURAT, Hanna Le Jeannic, Varun Verma, Adrien Cavaillès, Francesco Marsili, Matthew Shaw, Kun Huang, Olivier Morin, and Sae Woo Nam

Doc ID: 272418 Received 26 Jul 2016; Accepted 20 Oct 2016; Posted 21 Oct 2016  View: PDF

Abstract: We report on high-efficiency superconducting nanowire single-photon detectors based on amorphous WSi and optimized at 1064 nm. At an operating temperature of 1.8 K, we demonstrated a 93% system detection efficiency at this wavelength with a dark noise of a few counts per second. Combined with cavity-enhanced spontaneous parametric down-conversion, this fiber-coupled detector enabled us to generate narrowband single photons with a heralding efficiency greater than 90% and a high spectral brightness of 0.6.10⁴ photons/(s.mW.MHz). Beyond single-photon generation at large rate, such high-efficiency detectors open the path to efficient multiple-photon heralding and complex quantum state engineering.

Tunable Guided-Mode Resonance Filter of Gradient Grating Period Fabricated by Casting a Stretched PDMS Grating wedge

Dawei Zhang, Chaolong Fang, Bo Dai, Qi Wang, Zheng Li, ALI ZAHID, and Bing Sheng

Doc ID: 277712 Received 28 Sep 2016; Accepted 20 Oct 2016; Posted 20 Oct 2016  View: PDF

Abstract: A compact, tunable guided-mode resonant filter (GMRF) is proposed and experimentally demonstrated whose spectral reflectance wavelength varies as a function of the illumination position on the device. The GMRF consists of a grating of gradient-varying period ranging from 402.5 nm to 466.6 nm, which is obtained by casting a stretched polydimethylsiloxane (PDMS) grating wedge. By spatially changing the illumination position on the GMRF over 11 mm, a spectral reflectance peak with low sidelobes varies from 596.8 nm to 684.1 nm. The proposed GMRF is a good candidate as a functional filtering component in the wavelength selection and sensing applications.

Suppression of progressive growth of intensity modulations with slit spatial filter in a laser system

Zhenwu Zhuang, Xiao Yuan, Zhang Xiang, Muyu Yi, and han xiong

Doc ID: 277911 Received 03 Oct 2016; Accepted 19 Oct 2016; Posted 20 Oct 2016  View: PDF

Abstract: The performance of a slit spatial filter composed of two astigmatic lenses and two orthogonal slits for suppressing progressive growth of intensity modulations in a high power laser system was studied. Power spectral density (PSD) is used to evaluate the beam performance in the frequency domain. The filtering characteristics, image relay and beam expansion properties of the slit spatial filter are discussed and demonstrated. The experimental results show that the progressive growth of intensity modulations has been effectively suppressed with the slit spatial filter.

Two-phase SLIPI for instantaneous LIF and Mie imaging of transient fuel sprays

Michael Storch, Yogeshwar Nath Mishra, Matthias Koegl, Elias Kristensson, Stefan Will, Lars Zigan, and Edouard Berrocal

Doc ID: 277669 Received 04 Oct 2016; Accepted 19 Oct 2016; Posted 20 Oct 2016  View: PDF

Abstract: We report in this article, a two-phase Structured Laser Illumination Planar Imaging (2p-SLIPI) optical setup where the ‘’lines structure’’ is spatially shifted by exploiting the birefringence property of a calcite crystal.By using this optical component and two cross-polarized laser pulses, the shift of the modulated pattern is not “time-limited” anymore. Consequently, two sub-images with spatially mismatched phases can be recorded within a few hundred of nanoseconds only, freezing the motion of the illuminated transient flow. In comparison with previous setups for instantaneous imaging based on structured illumination, the current optical design presents the advantage of having a single optical path, greatly simplifying its complexity. Due to its virtue of suppressing the effects from multiple light scattering, the 2p-SLIPI technique is applied here in an optically dense multi-jet DISI (Direct-Injection Spark-Ignition) ethanol spray. The fast formation of polydispersed droplets and appearance of voids after fuel injection is investigated by simultaneous detection of Mie scattering and liquid Laser-Induced Fluorescence. The results allow for significantly improved analysis of the spray structure.

Watt-level fiber-based femtosecond laser source tunable from 2.8 to 3.6 µm

Simon Duval, Jean-Christophe Gauthier, Louis-Rafaël Robichaud, Pascal Paradis, Michel Olivier, Vincent Fortin, Martin Bernier, Michel Piche, and Real Vallee

Doc ID: 276472 Received 26 Sep 2016; Accepted 19 Oct 2016; Posted 19 Oct 2016  View: PDF

Abstract: The development of compact and reliable ultrafast sources operating in the mid-infrared region could lead to major advances in both fundamental and applied sciences. In this Letter, we report on a simple and efficient laser system based entirely on erbium-doped fluoride glass fibers that generates high-energy Raman soliton pulses tunable from 2.8 to 3.6 µm at a high average output power. Stable 160-fs pulses at 3.4 µm with a maximum energy of 37 nJ, a corresponding average output power above 2 W and an estimated peak power above 200-kW are demonstrated. This tunable source promises direct applications in laser processing of polymers and biological materials.

Design of a large field-of-view see-through near to eye display with two geometrical waveguides

jianming yang, Patrice Twardowski, Philippe Gerard, and Joël Fontaine

Doc ID: 266608 Received 19 May 2016; Accepted 19 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: A novel waveguide near to eye display (WGNED) with a new in-coupling and propagation subsystems is proposed for the first time to enlarge the field-of-view (FOV) and the eye box. Two waveguides are stacked, one is for in-coupling and the other for out-coupling. A freeform prism is used to correct the aberrations. These two components are combined together to form the WGNED. We have simulated such a system; as a result, we show that it achieves a FOV of 20°×60° and an eye box of about 15 ×12 mm. The modulation transfer function (MTF) of the system is larger than 0.3 at 33 lp/mm and the distortion is smaller than 4.5%.

Four-wave mixing parametric oscillation and frequency comb generation at visible wavelengths in a silica microbubble resonator

Yong Yang, Xuefeng Jiang, Lan Yang, Jonathan Ward, Sile Nic Chormaic, Sho Kasumie, Guangming Zhao, and Linhua Xu

Doc ID: 267986 Received 13 Jun 2016; Accepted 19 Oct 2016; Posted 19 Oct 2016  View: PDF

Abstract: Frequency comb generation in microresonators at visible wavelengths has found applications in a variety of areas such as metrology, sensing, and imaging. To achieve Kerr combs based on four-wave mixing in a microresonator, dispersion must be in the anomalous regime. In this work, we demonstrate dispersion engineering in a microbubble resonator (MBR) fabricated by a two-CO$_2$ laser beam technique. By decreasing the wall thickness of the MBR down to 1.4 $\mu$m, the zero dispersion wavelength shifts to values shorter than 764 nm, making phase matching possible around 765 nm. With the optical \textit{Q}-factor of the MBR modes being greater than $10^7$, four-wave mixing is observed at 765 nm for a pump power of 3 mW. By increasing the pump power, parametric oscillation is achieved, and a frequency comb with 14 comb lines is generated at visible wavelengths.

Interrogation of weak Bragg grating sensors based on dual-wavelength differential detection

Li Xia and Rui Cheng

Doc ID: 269225 Received 29 Jun 2016; Accepted 19 Oct 2016; Posted 19 Oct 2016  View: PDF

Abstract: It is shown that for weak Bragg gratings the logarithmic ratio of reflected intensities at any two wavelengths within the spectrum follow a linear relationship with the Bragg wavelength shift, with a slope proportionalto their wavelength spacing. This finding is exploited to develop a flexible, efficient and cheap interrogation solution of weak FBGs, especially for ultra-short FBGs, in distributed sensing based on dual-wavelength differential detection. The concept is experimentally studied in both single and distributed sensing systems with ultra-short FBG sensors. The work may form the basis of new and promising FBG interrogation techniques based on detecting discrete rather than continuous spectrum.

Spectral- and temporal- breathing self-similar evolution in fiber amplifier for low-noise transform-limited pulse generation

Bowen Liu, Sijia Wang, Wei Chen, Peng Qin, Youjian Song, and Ming-lie Hu

Doc ID: 274303 Received 24 Aug 2016; Accepted 19 Oct 2016; Posted 19 Oct 2016  View: PDF

Abstract: We demonstrate a simple scheme for the high-power low-noise high-contrast ultra-short pulse generation. It is enabled by the spectral- and temporal- breathing self-similar pulse evolution with an optimized negative pre-chirp. Experiments and simulations indicate the enhanced tolerances of this scheme to the gain-shaping distortions and pump fluctuations. It can lead to ~16% increase in the compressed pulse quality with more than 2 times wider spectrum and ~31% reduction in the root-mean-square (rms) relative intensity noise (RIN). Transform-limited pulses as short as 36 fs are generated with the rms RIN of 0.029% (1 kHz–5 MHz) from a 2-m Yb-fiber amplifier.

Mode-locked Yb-doped fiber laser emitting broadband pulses at ultra-low repetition rates

Patrick Bowen, Miro Erkintalo, Richard Provo, John Harvey, and Neil Broderick

Doc ID: 275813 Received 13 Sep 2016; Accepted 19 Oct 2016; Posted 19 Oct 2016  View: PDF

Abstract: We report on an environmentally stable, Yb-doped, all normal dispersion, mode-locked fibre laser that is capable of creating broadband pulses with ultra-low repetition rates. Specifically, through careful positioning of fibre sections in an all-PM-fibre cavity mode-locked with a nonlinear amplifying loop mirror, we achieve stable pulse trains with repetition rates as low as 506 kHz. The pulses have several nanojules of energy and are compressible down to ultrashort (< 500 fs) durations.

Dissipative four-wave mixing and Kerr combs in a bichromatically pumped nonlinear fiber ring cavity

Bertrand Kibler, Abdelkrim Bendahmane, Guy Millot, Julien Fatome, Davide Ceoldo, Stefan Wabnitz, Daniele Modotto, and Tobias Hansson

Doc ID: 274535 Received 02 Sep 2016; Accepted 18 Oct 2016; Posted 19 Oct 2016  View: PDF

Abstract: We report numerical and experimental studies of multiple four-wave mixing processes emerging from dual-frequency pumping of a passive nonlinear fiber ring cavity. We observe the formation of a periodic train of nearly-background-free soliton pulses associated with Kerr frequency combs. The generation of resonant dispersive waves is also reported.

Dielectric frame, Sellmeier equations and phase-matching properties of the Dielectric frame, Sellmeier equations and phase-matching properties of the monoclinic acentric crystal GdCa₄O(BO₃)₃

Patricia Segonds, Benoit Boulanger, Bertrand Ménaert, Jérôme Debray, Gerard Aka, Pascal Loiseau, and FENG GUO

Doc ID: 277730 Received 28 Sep 2016; Accepted 18 Oct 2016; Posted 19 Oct 2016  View: PDF

Abstract: We directly measured the phase-matching properties of the biaxial GdCa4O(BO3)3 crystal using the sphere method. We studied second harmonic generation and difference frequency generation in two principal planes of the crystal. All these data allowed us to refine the Sellmeier equations of the three principal refractive indices. These equations are valid over the entire transparency range of GdCOB and then could be used to calculate the tuning curves of infrared optical parametric generation.

Resolution enhancement of ghost imaging in atom vapor

Mingtao Cao, Xin Yang, Jinwen Wang, Shuwei Qiu, Dong Wei, Hong Gao, and fuli li

Doc ID: 278665 Received 13 Oct 2016; Accepted 18 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: The ghost imaging (GI) is an imaging technique in which the image of an object is revealed only in the correlation measurement between two beams of light, whereas the individual measurements contain no imaging information. Normally, the resolution of the image, which even exceeds the Rayleigh limit, is shown to be related to the transverse coherent length $({l_c})$ of the speckle pattern. In this letter, we demonstrated experimentally that the speckle size can be compressed by coherent population trapping (CPT) process in atom vapor, and the resolution of ghost imaging can be greatly enhanced by CPT process. The technique we exploit is quite efficient and robust, and it may be useful in the field of quantum and classical two-photon imaging, all-optical image processing, and quantum communication.

Frequency-doubled passively Q-switched microchip laser producing 225 ps pulses at 671 nm

Antti Harkonen, Jari Nikkinen, Ville Korpijärvi, Iiro Leino, and Mircea Guina

Doc ID: 270149 Received 08 Jul 2016; Accepted 18 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: We report a 671 nm laser source emitting 225 ps pulses with an average power of 55 mW and a repetition rate of 444 kHz. The system consists of a 1342 nm SESAM Q-switched Nd:YVO4 microchip master-oscillator and a dual-stage Nd:YVO4 power amplifier. The 1342 nm signal was frequency-doubled to 671 nm using a periodically poled lithium niobate crystal. This laser source provides a practical alternative for applications requiring high energy picosecond pulses, such as time-gated Raman spectroscopy.

Simultaneous Generation of Sub-5 Femtosecond 400 nm and 800 nm Pulses for Attosecond Extreme Ultraviolet Pump-Probe Spectroscopy

Hung-Tzu Chang, Michael Zuerch, Peter Kraus, Lauren Borja, Daniel Neumark, and Stephen Leone

Doc ID: 273714 Received 15 Aug 2016; Accepted 18 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: Few-cycle laser pulses with wavelengths centered at 400 nm and 800 nm are simultaneously obtained through wavelength separation of ultrashort, spectrally broadened Vis-NIR laser pulses spanning 350-1100 nm wavelengths. The 400 nm and 800 nm pulses are separately compressed, yielding pulses with 4.4 fs and 3.8 fs duration, respectively. The pulse energy exceeds 5 μJ for the 400 nm pulses and 750 μJ for the 800 nm pulses. Intense 400 nm few-cycle pulses have a broad range of applications in nonlinear optical spectroscopy, which include the study of photochemical dynamics, semiconductors, and photovoltaic materials on few-femtosecond to attosecond time scales. The ultrashort 400 nm few-cycle pulses generated here not only extend the spectral range of the optical pulse for NIR-XUV attosecond pump-probe spectroscopy but also pave the way for two-color, three-pulse, multi-dimensional optical-XUV spectroscopy experiments.

Peplography – A novel passive 3D photon counting imaging through scattering media

Myungjin Cho and Bahram Javidi

Doc ID: 274132 Received 19 Aug 2016; Accepted 18 Oct 2016; Posted 25 Oct 2016  View: PDF

Abstract: Dynamic imaging through scattering media under natural light is a significant challenge in many applications. To overcome this challenge, we propose a new passive imaging technique for scattering media using statistical estimation and photon counting modeling. We directly detect the ballistic photons emanating from objects in scattering media based on statistical optics and then show experimental results to support our proposed method. We have named the proposed technique “Peplography.” The word comes from Greek words πέπλο (péplo; “veiled”) and γραφής (grafís; “writing”). The peplography system directly detects ballistic photons associated with the objects from a single peplogram (“veiled image”) based on statistical optics, and reconstructing the three-dimensional (3D) peplogram using integral imaging.

Control of the state of a mode-locked fiber laser using an intracavity Martinez compressor

Kenneth Underwood and Juliet Gopinath

Doc ID: 273625 Received 11 Aug 2016; Accepted 17 Oct 2016; Posted 20 Oct 2016  View: PDF

Abstract: An intracavity Martinez compressor is incorporated into a fiber laser as a dispersion compensator and spectral filter. The Martinez compressor provides tunable dispersion from normal to anomalous. Inserting a mechanically adjustable slit into the compressor enables tunable spectral filtering independent of dispersion compensation. Mode-locking is achieved with bandwidths from 2.4 to 49.0 nm and compressor dispersions from +0.008 to -0.072 ps2. The laser generates stable pulses with 0.9 nJ pulse energy, a fundamental repetition rate of 77.5 MHz, and dechirped pulse widths as short as 86 fs.

Optical phase retrieval using conical refraction in structured media.

Evgenii Narimanov and Zun Huang

Doc ID: 274383 Received 29 Aug 2016; Accepted 17 Oct 2016; Posted 20 Oct 2016  View: PDF

Abstract: We propose a new method of optical phase retrieval based on the conical refraction imaging in structured media. We show that a multilayered dielectric photonic crystal functioning as a conically refractive flat lens can be used to reconstruct phase information of complex optical signals. Our method enables a single simulta- neous measurement of multiple images on the same im- age plane and allows a rapid stable recovery of the opti- cal phase. The planar geometry of the proposed device is compatible with current nano-fabrication techniques and therefore can find broad applications in optical sig- nal processing and imaging.

Single frame ultra-wide field lensless microscopy

Francois PERRAUT, Mickaël Doménès, Henri Grateau, and Quentin Josso

Doc ID: 274783 Received 30 Aug 2016; Accepted 17 Oct 2016; Posted 21 Oct 2016  View: PDF

Abstract: Lensless or lensfree Microscopy is now available commercially. With these new microscopes, it is possible to record images in contact mode with a magnification of 1 or in holographic mode with a magnification larger than 1. In this paper, we present an original setup that allows us to record the image of an object whose surface is larger than that of the image sensor without placing optical component between the object and the image sensor.

Radiation properties and hydrodynamics evolution of highly-charged ions in laser-produced silicon plasma

Chenzhong Dong, Qi Min, Maogen Su, Shiquan Cao, Duixiong Sun, and Gerard O'Sullivan

Doc ID: 275274 Received 08 Sep 2016; Accepted 17 Oct 2016; Posted 18 Oct 2016  View: PDF

Abstract: We present a simplified radiation hydrodynamic model based on the fluid dynamic equations and the radiative transfer equation, which can be used to investigate the radiation properties and dynamics evolution of highly-charged ions in a laser-produced plasma in vacuum. The outputs of the model consist of the evolution of electron temperature, atom and ion density, the temporal and spatial evolution of various transient particles in plasma, as well as the simulated spectrum related to certain experimental conditions in a specified spectral window. In order to test the model and provide valuable experimental feedback, a series of EUV emission spectra of silicon plasmas have been measured using the spatio-temporally resolved laser produced plasma technique. The temporal and spatial evolution of the plasma is reliably reconstructed by using this model.

A lossless and high-resolution RF photonic filter

Yang Liu, Amol Choudhary, David Marpaung, and Benjamin Eggleton

Doc ID: 275357 Received 07 Sep 2016; Accepted 17 Oct 2016; Posted 18 Oct 2016  View: PDF

Abstract: A novel technique to create a lossless and tunable RF photonic bandstop filter with ultra-high suppression is demonstrated using the combination of an over-coupled optical ring resonator and tailored stimulated Brillouin scattering (SBS) gain. The filter bandwidth narrowing is counter-intuitively synthesized from two broad optical resonance responses. Through precise amplitude and phase tailoring in the optical domain, the RF filter achieves minimum insertion loss (< 0 dB), a high isolation (>50 dB), and a tunable 3-dB bandwidth (60-220 MHz) simultaneously with wide frequency tunability (1-11 GHz). This ultra-low loss RF filter paves the way towards broadband advanced spectrum management with low loss, high selectivity and improved signal-to-noise ratio.

Fiber-coupled transceiver for terahertz reflection measurements with 4.5 THz bandwidth

Björn Globisch, Roman Dietz, Thorsten Göbel, Robert Kohlhaas, Simon Nellen, Moritz Kleinert, and Martin Schell

Doc ID: 277561 Received 26 Sep 2016; Accepted 17 Oct 2016; Posted 18 Oct 2016  View: PDF

Abstract: We present a fiber-coupled transceiver for THz time domain spectroscopy which combines emitter and receiver on a single photoconductive chip. With a bandwidth of 4.5 THz and a peak dynamic range larger than 70 dB it allows for THz reflection measurements under normal incidence. This THz reflection head is a promising device for applications in fields like material inspection and non-destructive testing.

Detecting the origin of luminescence in Er3+-doped hexagonal Na1.5Gd1.5F6 phosphors

Hyo Jin Seo, Yanyan Bu, Xiaohong Yan, Peiqing Cai, Jing Wang, ThiQuynh Vu, Xiangfu Wang, and Lin Qin

Doc ID: 273951 Received 17 Aug 2016; Accepted 17 Oct 2016; Posted 18 Oct 2016  View: PDF

Abstract: Understanding the site-selective fluorescence is one of valuable importance for spectrum modulation. In this letter, we observed the existence of two non-equivalent Gd-activated crystallographic sites in Er3+-doped hexagonal Na1.5Gd1.5F6 phosphor. It is proved that two green emissions from the 4S3/2 level separately originate from Gd1 (540 nm) and Na2/Gd2 (550-555 nm) crystallographic sites, and the 657 nm red emission from the 4F9/2 level only originates from Na2/Gd2 site, through using the dual-mode excitation source. The 142.2% absolute enhancement of the red emission is realized through the synergistic effect of ultraviolet down-conversion and infrared up-conversion induced by the 370 nm and 1.54 μm dual-mode excitation.

Few-cycle optical pulse characterization via cross-polarized wave generation dispersion scan technique

Ayhan Tajalli, Bruno Chanteau, Martin Kretschmar, Heiko Kurz, David Zuber, Milutin Kovacev, Uwe Morgner, and Tamas Nagy

Doc ID: 274912 Received 12 Sep 2016; Accepted 14 Oct 2016; Posted 18 Oct 2016  View: PDF

Abstract: We demonstrate a dispersion scan (d-scan) pulse characterization scheme employing cross-polarized wave (XPW) generation as a nonlinear optical process. XPW generation is a degenerate four-wave mixing process with no phase-matching limitations. Therefore, its implementation in d-scan method is an ideal choice for the characterization of few-cycle pulses in remote spectral regions. We fully characterize 5-10 fs pulses delivered through a hollow-core fiber in the near-IR region and compare the results with SHG FROG and SHG d-scan characterization methods.

Attenuated total reflection response to wavelength tuning of plasmon-induced transparency in a metal–insulator–metal structure

makoto tomita, KOUKI MATSUNAGA, Takeshi Watanabe, Yoichiro Neo, and Takahiro Matsumoto

Doc ID: 276118 Received 21 Sep 2016; Accepted 14 Oct 2016; Posted 14 Oct 2016  View: PDF

Abstract: We experimentally demonstrated plasmon-induced transparency in a metal–insulator–metal (MIM) structure based on the attenuated total reflection (ATR) response. Here, the MIM waveguide (MIMWG) mode and the surface plasmon polariton (SPP) resonance mode acted as low- and high Q resonance modes, respectively. The dependence of the resonance angles of SPP and MIMWG mode resonances on the incident wavelength differed, which allowed the coupling condition between the two modes to be tuned via the wavelength. When the resonance angles of the two modes coincided, the ATR response showed a symmetric plasmon-induced transparency spectrum; in contrast, when the resonance angles were detuned, the ATR exhibited a sharp asymmetric Fano spectrum.

Impact of Deposition-Rate Fluctuations on Thin-Film Thickness and Uniformity

James Oliver

Doc ID: 276234 Received 21 Sep 2016; Accepted 14 Oct 2016; Posted 14 Oct 2016  View: PDF

Abstract: Variations in deposition rate are superimposed on a thin-film–deposition model with planetary rotation to determine the impact on film thickness. Variations in magnitude and frequency of the fluctuations relative to the speed of planetary revolution lead to thickness errors and uniformity variations up to 3%. Sufficiently rapid oscillations in the deposition rate have a negligible impact, while slow oscillations are found to be problematic, leading to changes in the nominal film thickness. Superimposing noise as random fluctuations in the deposition rate has a negligible impact, confirming the importance of any underlying harmonic oscillations in deposition rate or source operation.

Two-dimensional non-reciprocal transmission in dynamically modulated photonic lattices

Xinyuan Qi, Shasha Li, Yang Lu, Kun Han, Jiachen Liu, Shuchao Lv, Pingan Gao, Xuanqi Feng, and Jintao Bai

Doc ID: 278587 Received 12 Oct 2016; Accepted 14 Oct 2016; Posted 19 Oct 2016  View: PDF

Abstract: We propose a method for realizing two-dimensional (2D) non-reciprocal (one-way) transmission of discretized light in a dynamically modulated optical waveguide array. By adjusting the phase of the modulation between the defect site and the most adjacent waveguides, asymmetric transmission in the same layer or between the first and third waveguide layers can be obtained. In particular, when the defect waveguide is lossless, 2D non-reciprocal transmission is realized perfectly.

60dB high-extinction auto-configured Mach--Zehnder interferometer

Callum Wilkes, Xiaogang Qiang, Jianwei Wang, Raffaele Santagati, Stefano Paesani, Xiao-Qi Zhou, David A. B. Miller, Graham Marshall, Mark Thompson, and Jeremy O'Brien

Doc ID: 275023 Received 01 Sep 2016; Accepted 13 Oct 2016; Posted 20 Oct 2016  View: PDF

Abstract: Imperfections in integrated photonics manufacturing have a detrimental effect on the maximal achievable visibility in interferometric architectures. These limits have profound implications for further photonics technological developments and in particular for quantum photonics technologies. Active optimisation approaches, together with reconfigurable photonics, have been proposed as a solution to overcome this. In this paper, we demonstrate an ultra-high (>60 dB) extinction ratio in a silicon photonic device consisting of cascaded Mach-Zehnder interferometers, in which additional interferometers function as variable beamsplitters. The imperfections of fabricated beamsplitters are compensated using an automated progressive optimization algorithm with no requirement for pre-calibration. This work shows the possibility of integrating and accurately controlling linear-optical components for large-scale quantum information processing and other applications.

Tuning laser plasma x-ray source for single shot microscopy using nano-porous targets

Reza Fazeli

Doc ID: 275764 Received 13 Sep 2016; Accepted 13 Oct 2016; Posted 17 Oct 2016  View: PDF

Abstract: Detailed calculations show that we can control and enhance line x-ray emission in the so called water-window wavelength region using laser irradiated nano-porous or foam-like targets. The effects of target porosity on the non-LTE plasma ionization are studied to obtain optimum conditions for maximum narrow band line emission. Results show that for specified irradiation conditions, the population of emitting ions can be significantly improved using a target with optimum initial mass density. In such conditions, efficient line x-ray can be emitted from the created plasma making it a suitable point flash source for high contrast x-ray imaging of living samples.

Multi-coherence-wavelength generation based on the monolithic integrated twin-microdisk lasers

Yong-Zhen Huang, Hai-Zhong Weng, Jin-Long Xiao, Yue-De Yang, Xiu-Wen Ma, Fu-Li Wang, and Yun Du

Doc ID: 275559 Received 08 Sep 2016; Accepted 13 Oct 2016; Posted 13 Oct 2016  View: PDF

Abstract: An effective method for multi-coherence-wavelength generation is experimentally demonstrated using the monolithic integrated twin-microdisk laser as a seed source. Dual-wavelength lasing with variable wavelength spacing is achieved by adjusting injection currents independently. Using the integrated chip as pumping seed, we generate the multi-coherence-wavelength in a nonlinear optical fiber, which has a tunable frequency interval from 50 to 300 GHz. Ten waves with optical signal to noise ratio larger than 10 dB are produced at the frequency interval of 200 GHz. The high signal noise ratio of autocorrelation trace and short pulse width of 1.2 ps indicate the high coherence in the mode-locked multi-wavelength.

1.5-14 μm mid-infrared supercontinuum generation in a low-loss Te-based chalcogenide step-index fiber

Xunsi Wang, zheming Zhao, Shixun Dai, Zhanghao Pan, Shuo Liu, Lihong Sun, Peiqing Zhang, Zijun Liu, Qiuhua Nie, Xiang Shen, and Rongping Wang

Doc ID: 273058 Received 03 Aug 2016; Accepted 13 Oct 2016; Posted 13 Oct 2016  View: PDF

Abstract: We experimentally demonstrated mid-infrared (MIR) supercontinuum (SC) generation in a low-loss Te-based chalcogenide (ChG) step-index fiber. The fiber fabricated by an isolated extrusion method has an optical loss of 2-3 dB/m at 6.2~10.3 μm and 3.2dB/m at 10.6 μm, the lowest value reported for any Te-based ChG step-index fiber. A MIR SC spectrum (~1.5 to 14 μm) is generated from the -cm fiber pumped by a 4.5 µm laser (~150 fs, 1kHz). To the best of our knowledge, this is the first SC experimental demonstration in Te-based ChG fiber and the broadest MIR SC generation pumping in the normal dispersion regime in the optical fibers.

Diode-pumped narrow linewidth multi-kW metalized Yb fiber amplifier

Charles Yu, Oleg Shatrovoy, Tso Yee Fan, and Thierry Taunay

Doc ID: 274221 Received 24 Aug 2016; Accepted 13 Oct 2016; Posted 13 Oct 2016  View: PDF

Abstract: We investigate high brightness pumping of a multi-kW Yb fiber amplifier in a bi-directional pumping configuration. Each pump outputs 2 kW in a 200 µm, 0.2 NA multi-mode fiber. Gold-coated specialty gain fibers, with 17 micron MFD and 5-dB/meter pump absorption, have been developed. The maximum fiber amplifier output power is 3.1 kW, limited by multi-mode instability, with 90% O-O efficiency and M2 < 1.15. The fiber amplifier linewidth is 12 GHz.

Theoretical analysis of ultra high-FOM sensing in plasmonic waveguides with a multimode stub

Hongjian Li, Zhihui He, Boxun Li, Zhiquan Chen, Hui Xu, and Mingfei Zheng

Doc ID: 274457 Received 24 Aug 2016; Accepted 12 Oct 2016; Posted 13 Oct 2016  View: PDF

Abstract: We propose an expanded coupled mode theory (CMT) to analysis sensing performance in a plasmonic slot waveguide side-coupled with a multimode stub resonator. It is confirmed by the finite-difference time-domain (FDTD) simulations. Through adjusting the parameters, we can realize figure of merit (FOM) of ~59010. Comparing with the plasmonic waveguide systems in recent articles, our proposed structure takes advantages of easy fabrication, compactness and high-FOM. The proposed theory model and findings provide guidance for fundamental research of the integrated plasmonic nanosensor applications.

Environment-Noise-Free Optical Heterodyne Retardation Measurement Using a Double-Pass Acousto-Optic Frequency Shifter

Che-Chung Chou, Tyson Lin, Sheng-Hua LU, Ru-Jong Jeng, and Shin-Yu Lu

Doc ID: 275474 Received 07 Sep 2016; Accepted 12 Oct 2016; Posted 13 Oct 2016  View: PDF

Abstract: We demonstrate an environment-noise-free optical heterodyne interferometer (OHI) based on a double-pass acousto-optics frequency shifter (AOFS) for phase retardation measurement.The OHI generates intermediate frequency (IF) heterodyne beat signals for each orthogonal linear polarization modes of a birefringence sample.The phase difference of IF signals is compared by using a wide bandwidth lock-in amplifier.This scheme provides 20 dB rejection of common mode environment disturbance.Measurements of half wave voltage of an electro-optics modulator and the electro-optic coefficient of a LiNbO$_3$ plate are demonstrated as the application examples.

Dynamics of Soliton Cascades in Fiber Amplifiers

Francisco Rodrigo Arteaga Sierra, Aku Antikainen, and Govind Agrawal

Doc ID: 269411 Received 30 Jun 2016; Accepted 12 Oct 2016; Posted 13 Oct 2016  View: PDF

Abstract: We study numerically the formation of cascading solitons when femtosecond optical pulses are launched into a fiber amplifier with less energy than required to form a soliton of equal duration. As the pulse is amplified, cascaded fundamental solitons are created at different distances, without soliton fission, as each fundamental soliton moves outside the gain bandwidth through the Raman-induced spectral shifts. As a result, each input pulse creates multiple, temporally separated, ultrashort pulses of different wavelengths at the amplifier output. The number of pulses depends not only on the total gain of the amplifier but also on the width of input pulses.

Long term stable coherent beam combination of independent femtosecond Yb-fiber lasers

Youjian Song, haochen tian, fei meng, Zhanjun Fang, Ming-lie Hu, and Qingyue Wang

Doc ID: 274144 Received 24 Aug 2016; Accepted 12 Oct 2016; Posted 13 Oct 2016  View: PDF

Abstract: We demonstrate coherent beam combination between independent femtosecond Yb-fiber lasers by using active phase locking of relative pulse timing and carrier envelope phase (CEP) based on balanced optical cross-correlator and extracavity acoustic optical frequency shifter, respectively. Broadband quantum noise of femtosecond fiber lasers is suppressed via precise cavity dispersion control, instead of complicated high bandwidth phase-locked loop design. Owing to reduced quantum noise and simplified phase locked loop, stable phase locking that lasts for 1 hour has been obtained, as verified via both spectral interferometry and far field beam interferometry. The approach can be applied to coherent pulse synthesis as well as remote frequency comb connection, allowing a practical all-fiber configuration.

Optical range-finding system using a single image sensor with liquid crystal display aperture

Joonki Paik, Sangwoo Park, Jinbeum Jang, and sangkeun lee

Doc ID: 272227 Received 25 Jul 2016; Accepted 12 Oct 2016; Posted 12 Oct 2016  View: PDF

Abstract: This letter presents an optical range-finding camera using a liquid crystal display (LCD) to generate multiple, off-axis color-filtered apertures in a flexible manner. Disparity between different color channels is measured from a pair of stereo images acquired by two offaxis apertures, and the distance of a scene point from the camera is then estimated from the pre-specified relationship between the color disparity and distance.

Time-slot coding scheme for multiple access in indoor optical wireless communications

Tian Liang, KE WANG, Christina Lim, Elaine Wong, Tingting Song, and Ampalavanapilla Nirmalathas

Doc ID: 274028 Received 24 Aug 2016; Accepted 12 Oct 2016; Posted 12 Oct 2016  View: PDF

Abstract: A novel time-slot coding (TSC) scheme is proposed in this paper to provide optical wireless communications to multiple users simultaneously with limited multi-user interference. The advantage of the proposed TSC is studied experimentally and results show that the code alignment tolerance, due to imperfect timing during the code generation process in practice, is 90.2%, 91.8 % and 93.1% with 4-QAM modulation at the received optical power of -22 dBm, -20 dBm and -18 dBm, respectively. Furthermore, a proof-of-concept experiment for simultaneous wireless connectivity for up to 5 users at multiple data rates (0.5 Gbps, 1 Gb/s, 1.6 Gb/s, 2 Gb/s, 2.5 Gb/s) is also demonstrated.

High power widely-tunable all-fiber thulium-assisted optical parametric oscillator at SWIR band

Can Li, Nan CHEN, Xiaoming Wei, Jiqiang Kang, Bowen Li, Sisi Tan, Liang Song, and Kenneth Kin-Yip Wong

Doc ID: 276064 Received 19 Sep 2016; Accepted 12 Oct 2016; Posted 19 Oct 2016  View: PDF

Abstract: A novel short-wave infrared (SWIR) all-fiber thulium-assisted optical parametric oscillator (TAOPO) that exploits jointly optical parametric conversion and thulium amplification in a highly-nonlinear fiber (HNLF) and thulium-doped fiber (TDF) is demonstrated. This is implemented through constructing a joint fiber line by directly fusion splicing 50 m HNLF with 1.5 m TDF. Incorporating a bidirectional-pumping scheme, i.e., forward-pumped by a step-tuned C-band pulsed laser, and simultaneously backward-pumped by an L-band continuous-wave laser, this TAOPO produces pulsed SWIR laser at output power higher than 200 mW, signal-to-noise ratio over 40 dB, and wavelength tuning range beyond 150 nm from 1815 nm to 1968 nm. Via separate characterization of the HNLF and TDF joint fiber line, the tunability of the current TAOPO to shorter wavelength is only limited by the employed fiber components, while higher power could be realized by increasing the backward pump power. This TAOPO could be a promising platform for the generation of highly functional SWIR source that facilitates applications such as bond-selective imaging of deep tissue.

Comparison of tomographic fluorescence spectral and lifetime multiplexing

Anand Kumar, Steven Hou, and Brian Bacskai

Doc ID: 273635 Received 12 Aug 2016; Accepted 11 Oct 2016; Posted 14 Oct 2016  View: PDF

Abstract: Multispectral and lifetime imaging in turbid media can be mathematically described in two steps, involving spectral or temporal mixing of fluorophores and diffuse light transport in the turbid medium. We show that the order of fluorophore mixing and diffuse propagation is reversed in spectral and lifetime multiplexing, resulting in a fundamental difference in their multiplexing capabilities, irrespective of measurement conditions. Using the resolution matrix to define a quantitative measure for inter-fluorophore cross-talk, we show that lifetime multiplexing, using the asymptotic time domain approach, provides zero cross-talk while spectral multiplexing can achieve zero cross-talk under special conditions. We also compare the performance of spectral and lifetime multiplexing for tomographic inversion of two overlapping fluorophores in a heterogeneous digital mouse atlas.

Investigation of noise-like pulses from a net normalYb-doped fiber laser based on a nonlinear polarizationrotation mechanism

Ja-Hon Lin, Chien-Lin Chen, Chen-Wei Chan, and Yao-Hui Chen

Doc ID: 274458 Received 01 Sep 2016; Accepted 11 Oct 2016; Posted 12 Oct 2016  View: PDF

Abstract: We investigated the characteristics of noise-like pulses(NLPs) from a passive mode-locked Yb-doped fiberlaser (YDFL) within a net normal dispersion regionwith the dispersion compensation by the grating pairs(GPs) inside the laser cavity. Without the insertion ofthe slit inside the laser cavity, the NLPs can be producedonce the YDFL is mode locked with the doublescale intensity autocorrelation trace (IAC) that canbe successfully compressed with the dispersion delayline outside the laser cavity. After inserting the slit insidebetween the GPs as a bandpass filter, the operationstate of the YDFL can switch between the NLPs to thedissipated solitons (DSs) by means of a pump power.Besides, the NLPs can also transit to the bound solitons(BSs) through the spatial shift of the slit to makethe YDFL operate within long and short wavelengthregimes.

High Speed and High Resolution Table-Top Nanoscale Imaging

Getnet Tadesse, Robert Klas, Stefan Demmler, Steffen Hadrich, Imam Wahyutama, Michael Steinert, Christian Spielmann, Michael Zuerch, Thomas Pertsch, Andreas Tünnermann, Jens Limpert, and Jan Rothhardt

Doc ID: 274539 Received 01 Sep 2016; Accepted 11 Oct 2016; Posted 12 Oct 2016  View: PDF

Abstract: We present a table-top coherent diffractive imaging (CDI) experiment based on high-order harmonics generated at 18 nm by a high average power femtosecond fiber laser system. The high photon flux, narrow spectral bandwidth and high degree of spatial coherence allow for ultra-high sub-wavelength resolution imaging at a high numerical aperture. Our experiments demonstrate a half-pitch resolution of 15 nm, close to the actual Abbe-limit of 12 nm, which is the highest resolution achieved from any table-top XUV or X-ray microscope. In addition, sub-30 nm resolution was achieved with only 3 sec of integration time bringing live diffractive imaging and 3D tomography on the nanoscale one step closer to reality. The current resolution is solely limited by the wavelength and the detector size. Thus, table-top nanoscopes with only a few-nm resolutions are in reach and will find applications in many areas of science and technology.

Intracavity measurement of the electro-optic Kerr effectvia carrier envelope phase demodulation

Tianli Feng, Nils Raabe, Pascal Rustige, and Gunter Steinmeyer

Doc ID: 272718 Received 28 Jul 2016; Accepted 11 Oct 2016; Posted 12 Oct 2016  View: PDF

Abstract: Placing a sinusoidally driven air capacitor in theintracavity beam path of a mode-locked few-cycleTi:sapphire oscillator, we measure the influence ofthe electro-optical Kerr effect on the carrier-envelopephase of the laser pulses. Using a capacitor length ofonly 8 cm at atmospheric pressure, we observe a Kerrinducedfrequency modulation of the carrier-envelopebeatnote. From the measured frequency excursion,we determine a Kerr constant on the order of 10􀀀27m2/V2, which is found to agree with theoretically computedhyperpolarizabilities of the nitrogen and oxygenmolecules. The carrier-envelope phase only dependson the dispersion of the hyperpolarizability, which hasbeen previously found very challenging to measure inthe gas phase. Our substantially more sensitive measurementmethod for the electro-optic Kerr effect inair may prove a valuable tool for non-contact measurementsof high voltages in power grids and even formonitoring atmospheric electric fields during thunderstorms.

Compressive 4D Spectro-Volumetric Imaging

yaniv oiknine, Yitzhak August, Adrian Stern, and Vladimir Farber

Doc ID: 270548 Received 14 Jul 2016; Accepted 10 Oct 2016; Posted 11 Oct 2016  View: PDF

Abstract: In this letter, we present a method for hyperspectral imaging of three dimensional objects. A compressive sensing approach is utilized to remedy the acquisition effort required to capture the large amount of data. The spectral dimension is compressively sensed by means of a liquid crystal-based encoder and the volumetric data is captured using a synthetic aperture integral imaging setup. We demonstrate reconstruction of spectro-volumetric tesseracts with hundreds of spectral bands at different depths without compromise of spatial resolution.

Realisation of High Contrast Gratings operating at 10 μm

Brian Hogan, Stephen Hegarty, Liam Lewis, javier Romero-Vivas, Tomasz Ochalski, and Guillaume Huyet

Doc ID: 274102 Received 31 Aug 2016; Accepted 10 Oct 2016; Posted 11 Oct 2016  View: PDF

Abstract: We present a new material pairing which can be used to realise high contrast gratings at wavelengths of 10 μm and greater. Using only optical lithography, the material pair solves the absorption issue limiting the popular Si\SiO₂ pairing from operation above 6 μm. We describe the obstacles that exists with the currently used grating materials for this wavelength range and outline why our chosen materials overcome this obstacle. We numerically demonstrate that gratings utilising these materials are capable of wideband high reflectivity. We experimentally show that the spectral response of gratings which are fabricated using such a process show good agreement with theoretically predicted performance.

High resolution, large dynamic range fiber-optic thermometer with cascaded silicon Fabry-Perot cavities

Ming Han, Qiwen Sheng, Guigen Liu, and Weilin Hou

Doc ID: 274587 Received 29 Aug 2016; Accepted 10 Oct 2016; Posted 11 Oct 2016  View: PDF

Abstract: The paradox between large dynamic and high resolution commonly exists in nearly all kinds of sensors. Here, we propose a fiber-optic thermometer based on dual silicon Fabry-Perot interferometers (FPIs) made from the same material but with different cavity lengths, which combines the large dynamic range of the thin FPI and the high resolution of the thick FPI. To verify this new concept, a sensor with one 200 μm thick silicon FPI cascaded by another 10 μm thick silicon FPI was fabricated. Measurements over temperature range of −50 to 130 ºC with a resolution of 6.8×10^−3 ºC was demonstrated. Compared to a sensor with only the thick silicon FPI, the dynamic range of the hybrid sensor was more than 10 times larger. Compared to a sensor with only the thin silicon FPI, the resolution of the hybrid sensor was more than 18 times higher, which was limited by the noise of the optical interrogator.

Optical vortex coronagraphy from soft spin-orbit masks

Etienne Brasselet and Artur Aleksanyan

Doc ID: 274755 Received 29 Aug 2016; Accepted 10 Oct 2016; Posted 11 Oct 2016  View: PDF

Abstract: We report on a soft route towards optical vortex coronagraphy based on self-engineered electrically tunable vortex masks based on liquid crystal topological defects. These results suggest that a Nature-assisted technological approach to the fabrication of complex phase masks could be useful in optical imaging whenever optical phase singularities are at play.

Coherence for vectorial waves and majorization

Alfredo Luis

Doc ID: 275284 Received 07 Sep 2016; Accepted 10 Oct 2016; Posted 11 Oct 2016  View: PDF

Abstract: We show that majorization provides a powerful tool to examine the coherence conveyed by partially polarized electromagnetic waves.

Stable vortex solitons in a ring-shaped partially-parity-time symmetric potential

Liangwei Dong and Changming Huang

Doc ID: 275838 Received 14 Sep 2016; Accepted 10 Oct 2016; Posted 11 Oct 2016  View: PDF

Abstract: We address the existence and stability of vortex solitons in a ring-shaped partially-parity-time ($\text{p}\mathcal{PT}$) configuration. In sharp contrast to the reported nonlinear modes in $\mathcal{PT}$- or $\text{p}\mathcal{PT}$-symmetric systems, stable vortex solitons with different topological charges can be supported by the proposed $\text{p}\mathcal{PT}$ potential, despite that the system is always beyond the symmetry-breaking point. Vortex solitons are characterized by the number of phase singularities which equals to the corresponding topological charge. At higher power, unstable higher-charged vortices degenerate into stable vortices with lower charges. Robust nonlinear vortices can be easily excited by an input Gaussian beam. Our results provide the first example of stable solitons in a symmetry-breaking system.

Micro-pulse upconversion Doppler lidar for wind and visibility detection in the atmospheric boundary layer

Xiankang Dou, Haiyun Xia, Mingjia Shangguan, Chong Wang, Guoliang Shentu, Jiawei Qiu, Qiang Zhang, and Jian-Wei Pan

Doc ID: 274371 Received 24 Aug 2016; Accepted 10 Oct 2016; Posted 13 Oct 2016  View: PDF

Abstract: For the first time, a versatile, eyesafe, compact and direct detection Doppler lidar is developed using upconversion single-photon detection method at 1.5 . An all-fiber and polarization maintaining architecture is realized to guarantee the high optical coupling efficiency and the system stability. Using integrated-optic components, the conservation of etendue of the optical receiver is achieved by manufacturing a fiber-coupled periodically poled Lithium niobate waveguide and an all-fiber Fabry-Perot interferometer (FPI). The double-edge technique is implemented using a single-channel FPI and a single upconversion detector, incorporating time-division multiplexing method. The backscatter photons at 1548.1 nm are converted into 863 nm ones, with a pump wavelength of 1950 nm. The relative error of the system is lower than 0.1% over 9 weeks. Atmospheric wind and visibility over 48 hours are detected in the boundary layer. In experiments, lidar shows good agreement with the ultrasonic wind sensor, with standard deviation of 1.04 m/s in speed and 12.3 degree in direction.

Surface wave illumination Fourier ptychographic microscopy

Cuifang Kuang, Qiulan Liu, Yue Fang, Renjie Zhou, Peng Xiu, and Xu Liu

Doc ID: 274403 Received 29 Aug 2016; Accepted 10 Oct 2016; Posted 13 Oct 2016  View: PDF

Abstract: We propose a novel microscopy method, combining surface wave illumination and the Fourier ptychographic microscopy (FPM) algorithm, to achieve super-resolution imaging. In our system, an oil-immersion objective lens is used to excite both the total internal reflection (TIR) evanescent waves and the surface plasmon waves (SPWs), which illuminate the sample with large wave vectors. Through the FPM algorithm, a resolution approximately twice that of conventional wide-field microscopy is obtained. Meanwhile, we could retrieve the sample’s quantitative phase map in order to obtain its surface profile. Importantly, the field enhancement from SPW has improved the contrast of the reconstructed images, which is critical for revealing the finer structural details of the specimen. In our experiments, we have imaged metallic gratings with 120 nm or 150 nm wide line and trench features. We can accurately retrieved their axial dimension with lateral resolution better than 240 nm that is close to the theoretical resolution of 215 nm, thus demonstrating the quantitative phase imaging capability of our technique. As this approach provides a label-free solution for intensity and phase imaging of samples with lateral resolution exceeding the limit introduced by the optical system, it can be potentially used in a wide range of noninvasive biological imaging applications.

On speckle suppression in IR Digital Holography

Pasquale Memmolo, Vittorio Bianco, Melania Paturzo, and Pietro Ferraro

Doc ID: 273160 Received 04 Aug 2016; Accepted 09 Oct 2016; Posted 13 Oct 2016  View: PDF

Abstract: Long-IR wavelength is the best option for capturing digital holograms of large size, real-world objects. However, the coherent noise level in a long-IR hologram is by far larger than that of a visible wavelength recording, thus resulting in a poor quality of both numerical and optical reconstructions. In this paper, we show how such coherent-noise can be efficiently suppressed by employing an optical scanning Multi-Look approach in combination with the 3D Block Matching (BM3D) numerical filtering. Results demonstrate the possibility to obtain near noise-free numerical reconstructions of IR digital holograms of large size objects, while preserving resolution. We applied this novel method to the holograms of a rotating statuette. It will be shown that a remarkable contrast enhancement is achievable along with the recovery of object details, that otherwise would be lost because of large speckle grains intrinsically due to the source coherence.

Spectral and fluorescence lifetime endoscopic system using a double-clad photonic crystal fiber

Ali ibrahim, Fanny POULON, Fatima MELOUKI, marc zanello, Pascale Varlet, Remi Habert, Pr devaux, Alexandre Kudlinski, and Darine Abi Haidar

Doc ID: 270709 Received 03 Aug 2016; Accepted 09 Oct 2016; Posted 12 Oct 2016  View: PDF

Abstract: We present a customized small-core double-clad photonic crystal fiber for spectral and fluores-cence lifetime measurements of human samples. In this study the new fiber has been character-ized on different fluorophores, samples of hu-man brain tumor, and a comparison to a bi-fiber homemade system and a commercial fiber probe was made.

Heteroclinic dynamics of coupled semiconductor lasers with optoelectronic feedback

Shiva Shahin, Felipe Vallini, Faraz Monifi, Michail Rabinovich, and Yeshaiahu Fainman

Doc ID: 276099 Received 19 Sep 2016; Accepted 09 Oct 2016; Posted 14 Oct 2016  View: PDF

Abstract: Generalized Lotka-Volterra (GLV) equations is an important set of equations used in various areas of science to describe competitive dynamics among a population of N interacting nodes in a network topology. In this manuscript, we introduce a photonic network consisting of three optoelectronically cross-coupled semiconductor lasers to realize a GLV model. In such a network, the interaction of intensity and carrier inversion rates as well as phases of laser oscillator nodes result in various dynamics. We study the influence of asymmetric coupling strength and frequency detuning between semiconductor lasers and show that inhibitory asymmetric coupling is required to achieve consecutive amplitude oscillations of laser nodes. These studies were motivated primarily by the dynamical models used to model brain cognitive activities and their correspondence with dynamics obtained among coupled laser oscillators.

Picosecond green and deep ultraviolet pulses generated by a high-power 100 kHz thin-disk laser

Ondrej Novak, Hana Turčičová, Martin Smrz, Taisuke Miura, Akira Endo, and Tomas Mocek

Doc ID: 276026 Received 19 Sep 2016; Accepted 09 Oct 2016; Posted 13 Oct 2016  View: PDF

Abstract: We report on the generation of the second (515 nm) and fourth (257.5 nm) harmonics from a 100 kHz diode-pumped solid-state laser (DPSSL) operated at a wavelength of 1030 nm which uses one Yb:YAG thin disk in the regenerative amplifier and delivers 60 W of the average output power in pulses of 4 ps duration. 35 W in the green light and 6 W in deep ultraviolet (DUV) were achieved. The sensitivity of the SHG efficiency towards the LBO crystal temperature is demonstrated in experiment. The overall conversion efficiency from NIR to DUV of 10 % was achieved. The BBO and CLBO crystals were used as green to DUV convertors and compared regarding the efficiency and spectral bandwidths. The achieved output power is unique for DUV picosecond pulses.

About 400 kW Peak-Power, 6.3 GHz Linewidth, 1.5 μm Fiber Gas Raman Source

Yubin Chen, Zefeng Wang, Bo Gu, Fei Yu, and Qisheng Lu

Doc ID: 272153 Received 22 Jul 2016; Accepted 09 Oct 2016; Posted 10 Oct 2016  View: PDF

Abstract: Due to various nonlinear effects in Er-doped or Er-Yb co-doped solid-core fibers at high power, it is quite difficult to achieve 1.5 μm fiber laser emission of both high peak-power and narrow linewidth, which is required in some applications. Here, we demonstrated for the first time a novel and effective method for obtaining both high peak-power and narrow linewidth 1.5 μm fiber source through gas Raman effect in hollow core fibers. An Ethane-filled ice-cream anti-resonance hollow-core fiber is pumped with a high peak-power pulse 1064 nm microchip laser, generating 1552.7 nm Stokes wave by pure vibrational stimulated Raman scattering of ethane molecules. A maximum peak-power of about 400 kW is achieved with 6 meter fiber length at 2 bar pressure. The maximum Raman conversion efficiency of 1064 nm to 1552.7 nm is about 38%, and the corresponding laser slope efficiency is about 61.5%. The linewidth of the Stokes wave is about 6.3 GHz, finely measured using a scanning Fabry-Perot interferometer. Comparing with the traditional 1.5 μm Er-doped or Yb-Er co-doped fiber lasers, the peak power is increased 1~2 orders of magnitude, meanwhile the linewidth is decreased 1~2 orders of magnitude. If using a tunable pump laser, this kind of fiber source can easily achieve broad tuning range near 1.5 μm.

Technique for suppressing the electronic offset drift of interferometric open-loop fiber optic gyroscopes

Rodrigo Bacurau, Anderson Spengler, Alex Dante, Flávio Morais, Luis Duarte, Luiz Ribeiro, and Elnatan Ferreira

Doc ID: 268472 Received 17 Jun 2016; Accepted 08 Oct 2016; Posted 10 Oct 2016  View: PDF

Abstract: A technique to eliminate the offset drift in the demodulator circuitry of open-loop interferometric fiber optic gyroscopes is presented. This technique employs a demodulation scheme that uses the area of the negative half-cycles of the sinusoidally-modulated gyroscope signal to obtain the angular velocity. We propose an electronic circuitry that periodically reverses the demodulator input, allowing for the acquisition of two samples of the gyroscope signal with same magnitude and opposite polarities. The angular velocity is obtained from the subtraction of these two samples, suppressing the electronic offset. Experiments showed that the proposed method reduces the demodulator offset drift from 4.4 μV/°C to about 14 nV/°C, which is equivalent to a reduction, from 0.2 deg/h/°C to about 0.0006 deg/h/°C in the tested gyroscope. The proposed technique improved the bias stability of the tested gyroscope from 0.0162 deg/h to 0.0071 deg/h.

Optical limiting by nonlinear tuning of resonance in metamaterial absorbers

Sriram Guddala and S. Anantha Ramakrishna

Doc ID: 275659 Received 14 Sep 2016; Accepted 07 Oct 2016; Posted 07 Oct 2016  View: PDF

Abstract: Metamaterial resonant absorbers (MRA) have intense local field enhancements that can be used to elicit large nonlinear responses. An MRA, composed of gold disks separated by a ZnS thin film from an underlying gold layer, shows optical limiting for the reflectivity of 8 ps pulses at 1064 nm due to the Kerr nonlinearity of gold and ZnS. Fluorescence from multi-photon absorption due to large fields localized in the ZnS layer is measured, and the effective χ(3) of the layer is enhanced by three orders of magnitude compared to bare ZnS thin films. Self-consistent nonlinear electromagnetic simulations confirm that the nonlinear absorption is caused by a shift of the resonance with increasing intensity.

Photonic crystals with broadband, wide-angle and polarization-insensitive transparency

Yun Lai, Zhongqi Yao, and jie luo

Doc ID: 275883 Received 20 Sep 2016; Accepted 07 Oct 2016; Posted 07 Oct 2016  View: PDF

Abstract: Photonic crystals are well-known band gap materials that can block the propagation of electromagnetic waves within certain frequency regimes. Here, we demonstrate that photonic crystals can also exhibit the contrary property: broadband, wide-angle and polarization-insensitive transparency beyond normal dielectric solids. Such high transparency attributes to robust impedance matching between certain modes in photonic crystals with propagating waves in free space. As a demonstration, a transparent wall for broadband microwaves is designed for enhancing the transmittance of WiFi and 4G signals.

Toward an integrated device for spatio-temporal superposition of FEL and laser pulses

Riccardo Mincigrucci, Alessia Matruglio, Andrea Calvi, Laura Foglia, Emiliano Principi, Alberto Simoncig, Filippo Bencivenga, Stefano Dallorto, Alessandro Gessini, Gabor Kurdi, Deirdre Olynick, Scott Dhuey, Rudi Sergo, Marco Lazzarino, Claudio Masciovecchio, and Simone Dal Zilio

Doc ID: 276087 Received 20 Sep 2016; Accepted 07 Oct 2016; Posted 07 Oct 2016  View: PDF

Abstract: Nowadays free electron lasers (FELs) permit to push forward time resolved investigations on condensed materials through pump-probe methods involving FEL and laser beams. That class of experiments requires an accuratespatial and temporal superposition of pump and probe beams on the sample, which at the present is still a critical procedure. More efficient approaches are demanded to quickly achieve beams superposition and synchronization. Here, we present a novel technique based on an integrated device allowing the simultaneous characterization and thefast spatial and temporal overlapping of the beams, reducing the alignment procedure from hours to minutes.

Clustered Frequency Comb

Andrey Matsko, Anatoliy Savchenkov, Shu-Wei Huang, and Lute Maleki

Doc ID: 273933 Received 16 Aug 2016; Accepted 06 Oct 2016; Posted 06 Oct 2016  View: PDF

Abstract: We show theoretically that it is feasible to generate a spectrally broad Kerr frequency comb consisting of several spectral clusters phase matched due to interplay among second and higher orders group velocity dispersion contributions. We validate the theoretical analysis experimentally by driving a magnesium fluoride resonator, characterized with 110 GHz free spectral range, with a continuous wave light at 1.55 μm and observing two comb clusters separated by nearly a 2/3 of octave.

Spectral correlation and interference in non-degenerate photon pairs at telecom wavelengths

Paulina Kuo, Thomas Gerrits, Varun Verma, and Sae Woo Nam

Doc ID: 272564 Received 24 Aug 2016; Accepted 06 Oct 2016; Posted 07 Oct 2016  View: PDF

Abstract: We characterize an entangled photon pair source that produces signal and idler photons at 1533 nm and 1567 nm using fiber-assisted signal-photon spectroscopy. By erasing the polarization distinguishability, we observe interference between the two down-conversion paths. The observed interference signature is closely related to the spectral correlations between photons in a Hong-Ou-Mandel interferometer. These measurements suggest good indistinguishability between the two down-conversion paths, which is required for high entanglement visibility.

Nondestructive Measurement of the Roughness of the Inner Surface of Hollow Core-Photonic Bandgap Fibers

Gilles Tessier, Xavier Buet, Coralie Brun, Jérôme Gateau, Bruno Bresson, Seyed Reza Sandoghchi, Eric Rodrigue Numkam Fokoua, Marco Petrovich, Francesco Poletti, David Richardson, and Damien Vandembroucq

Doc ID: 272697 Received 30 Aug 2016; Accepted 06 Oct 2016; Posted 07 Oct 2016  View: PDF

Abstract: We present optical and atomic force microscopy measurements of the roughness of the core wall surface within a Hollow Core Photonic Bandgap Fiber (HC-PBGF) over the [3×10-2 µm-1 – 30 µm-1] spatial frequency range. A recently developed immersion optical profilometry technique with picometer-scale sensitivity was used to measure the roughness of air-glass surfaces inside the fiber at unprecedentedly low spatial frequencies, which are known to have the highest impact on HC-PBGF scattering loss and thus determine their loss limit. Nondestructive optical access to the inner surface of the core was obtained by selective filling of the cladding holes with index matching liquid using techniques borrowed from micro-fluidics. Both measurement techniques reveal ultra-low roughness levels exhibiting a 1/f spectral power density dependency characteristic of frozen surface capillary waves over a broad spatial frequency range. However, a deviation from this behavior at low spatial frequencies was observed for the first time.

Optical parametric generation by a simultaneously Q-switched mode-locked single-oscillator thulium-doped fiber laser in Orientation-Patterned Gallium Arsenide

Brenda Donelan, Christian Kneis, Giuseppe Scurria, Benoit Cadier, thierry Robin, Eric Lallier, Arnaud Grisard, Bruno Gerard, Marc Eichhorn, and Christelle Kieleck

Doc ID: 273549 Received 24 Aug 2016; Accepted 06 Oct 2016; Posted 07 Oct 2016  View: PDF

Abstract: Optical parametric generation is demonstrated in orientation-patterned gallium arsenide, pumped by a novel single oscillator simultaneously Q-switched and mode-locked thulium-doped fiber laser, down-converting the pump radiation into the mid-infrared. The maximum output energy reached is greater than 2.0 μJ per pump pulse.

Difference frequency generation in the mid-infrared with orientation-patterned gallium phosphide crystals

Cecilia Clivati, Giacomo Insero, Davide D'Ambrosio, Paolo De Natale, Gabriele Santambrogio, Peter Schunemann, Jean-Jacques Zondy, and Simone Borri

Doc ID: 274343 Received 24 Aug 2016; Accepted 06 Oct 2016; Posted 07 Oct 2016  View: PDF

Abstract: We report on the generation of coherent mid-infrared radiation around 5.85 μm by difference frequency generation (DFG) of continuous-wave Nd:YAG laser at 1064 nm and diode-laser at 1301 nm in an orientation-patterned gallium phosphide (OP-GaP) crystal. We provide the first characterization of the linear, thermo-optic and nonlinear properties of OP-GaP in a DFG configuration. Moreover, by comparing the experimental efficiency to Gaussian beam DFG theory, we derive an effective nonlinear coefficient d = 17(3) pm/V for first-order quasi-phase-matched OP-GaP. The temperature and signal-wave tuning curves are in qualitative agreement with theoretical modeling.

Colossal magneto-optical modulation at terahertz frequencies by counterpropagating femtosecond laser pulses in Tb₃Ga₅O₁₂

Rostislav Mikhaylovskiy, Ruslan Subkhangulov, Theo Rasing, and A. Kimel

Doc ID: 267877 Received 08 Jun 2016; Accepted 06 Oct 2016; Posted 06 Oct 2016  View: PDF

Abstract: Single-frequency terahertz modulation of the magneto-optical Faraday effect with a record amplitude of the polarization rotation of ~0.5⁰ is achieved using a slab of the etalon Faraday rotator crystal, Tb₃Ga₅O₁₂. The modulation is the result of the interaction of two counter-propagating laser pulses via the optical Kerr effect. The frequency of the modulation is determined by the applied magnetic field and is continuously tunable in the terahertz frequency range between 0 and 0.7 THz.

Tunable single- and dual-wavelength SHG from diode-pumped PPKTP waveguides

Ksenia Fedorova, CHRISTINE WONG, CHRISTOPHER KALEVA, ILIA BAKSHAEV, Daniil Livshits, and Edik Rafailov

Doc ID: 272248 Received 26 Jul 2016; Accepted 05 Oct 2016; Posted 06 Oct 2016  View: PDF

Abstract: A compact, all-room-temperature, widely-tunable, continuous wave (CW) laser source in the green spectral region (502.1 nm – 544.2 nm) with a maximum output power of 14.7 mW is demonstrated. This was made possible by utilizing second-harmonic generation (SHG) in a periodically poled potassium titanyl phosphate (PPKTP) crystal waveguide pumped by a quantum-well external-cavity fiber-coupled diode laser and exploiting the multimode-matching approach in nonlinear crystal waveguides. The dual-wavelength SHG in the wavelength region between 505.4 nm and 537.7 nm (with a wavelength difference ranging from 1.8 nm to 32.3 nm) and sum-frequency generation in a PPKTP waveguide is also demonstrated.

Ultra-broadband dual-mode 3 dB power splitter based on a Y-junction assisted with mode converters

Hongnan Xu and Yaocheng Shi

Doc ID: 272368 Received 26 Jul 2016; Accepted 05 Oct 2016; Posted 06 Oct 2016  View: PDF

Abstract: A dual-mode 3 dB power splitter for application of on-chip mode (de)multiplexing system is proposed and demonstrated. This device is composed of mode converters cascaded with a Y-junction. The simulation results show that ~50:50 splitting ratio can be achieved for both TM0 mode and TM1 mode over a wide wavelength range from 1.52 μm to 1.62 μm. The fabricated device, which consists of a multiplexer, a dual-mode 3 dB power splitter and a demultiplexer, has insertion losses of 0.54 dB for TM0 mode and 0.86 dB for TM1 mode at 1.55 μm wavelength. The measured crosstalk is 15.7 dB and 17.2 dB at 1.55 μm wavelength for TM0 mode and TM1 mode, respectively.

Experimental demonstration of graphene plasmons working close to the near-infrared window

Sanshui Xiao, Zhongli Wang, Tao Li, N. Asger Mortensen, Sokol Ndoni, and Kristoffer Almdal

Doc ID: 275351 Received 06 Sep 2016; Accepted 05 Oct 2016; Posted 06 Oct 2016  View: PDF

Abstract: Due to strong mode-confinement, long propagation-distance, and unique tunability, graphene plasmons have been widely explored in the mid-infrared and terahertz windows. However, it remains a big challenge to push graphene plasmons to shorter wavelengths in order to integrate graphene plasmon concepts with existing mature technologies in the near-infrared region. We investigate localized graphene plasmons supported by graphene nanodisks and experimentally demonstrated graphene plasmon working at 2 um with the aid of a fully scalable block copolymer self-assembly method. Our results show a promising way to promote graphene plasmons for both fundamental studies and potential applications in the near-infrared window.

A framework to trade optimality for local processing in large-scale wave-front reconstruction problems

Aleksandar Haber and Michel Verhaegen

Doc ID: 275730 Received 12 Sep 2016; Accepted 05 Oct 2016; Posted 06 Oct 2016  View: PDF

Abstract: We show that the minimum variance wave-front estimation problems permit localized approximate solutions, in the sense that the wave-front value at a point can be approximated by a linear combination of the wave-front slope measurements in the point's neighborhood. This enables us to efficiently compute a wave-front estimate by performing a single sparse matrix-vector multiplication. Moreover, our results open the possibility for the development of the wave-front estimators that can be easily implemented in a decentralized/distributed manner, and in which the estimate optimality can be easily traded for the computational efficiency. Such a computationally efficient estimate can also be used as an initial estimate for other wave-front reconstruction algorithms. We numerically validate our approach on Hudgin wave-front sensor geometries, and the results can be easily generalized to Fried geometries.

Gaussian entanglement distribution with gigahertz bandwidth

Stefan Ast, Roman Schnabel, Melanie Ast, and Moritz Mehmet

Doc ID: 278184 Received 05 Oct 2016; Accepted 05 Oct 2016; Posted 06 Oct 2016  View: PDF

Abstract: The distribution of entanglement with Gaussian statis-tic can be used to generate a mathematically-proven se-cure key for quantum cryptography. The distributedsecret key rate is limited by the entanglement strength,the entanglement bandwidth and the bandwidth of thephoto-electric detectors. The development of a sourcefor strongly, bi-partite entangled light with high band-width promises an increased measurement speed and alinear boost in the secure data rate. Here, we present theexperimental realization of a Gaussian entanglementsource with a bandwidth of more than 1.25 GHz. Theentanglement spectrum was measured with balancedhomodyne detectors and was quantified via the insep-arability criterion introduced by Duan and coworkerswith a critical value of 4 below which entanglementis certified. Our measurements yielded an insepara-bility value of about 1.8 at a frequency of 300 MHz toabout 2.8 at 1.2 GHz extending further to about 3.1 at1.48 GHz. In the experiment we used two 2.6 mm longmonolithic periodically poled KTP resonators to gener-ate two squeezed fields at the telecommunication wave-length of 1550 nm. Our result proves the possibilityof generating and detecting strong continuous-variableentanglement with high speed.

Simple production of membrane-based LiNbO3 micro-modulators with integrated tapers

Nadège COURJAL, Alexis Caspar, Venancio Calero, gwenn ulliac, Miguel Suarez, Clément Guyot, and Maria-Pilar Bernal

Doc ID: 273831 Received 06 Sep 2016; Accepted 05 Oct 2016; Posted 10 Oct 2016  View: PDF

Abstract: We report on free-standing electro-photonic LiNbO3 waveguides with integrated tapers made by optical grade dicing. Membranes with a calibrated thickness are produced simultaneously with tapers acting as spot-size converters. Thereby, thicknesses from 450 nm to 500 µm can simply be achieved together with integrated tapers guaranteeing low insertion losses. These developments open the way to the low-cost production of compact and low-power-consuming electro-photonic components. As an example, a 200 µm-long free-standing electro-photonic Fabry-Perot is demonstrated with a figure of merit of only 0.19 V·cm in a 4.5 µm-thick membrane.

Manipulation of Beat Length and Wavelength Dependence of a Polarization Beam Splitter Using Subwavelength Grating

Zhiping Zhou, Lu Liu, and Qingzhong Deng

Doc ID: 275256 Received 05 Sep 2016; Accepted 05 Oct 2016; Posted 10 Oct 2016  View: PDF

Abstract: A polarization beam splitter assisted by subwavelength grating (SWG) is proposed. The SWG enables nearly 20-fold beat length reduction for TE, which makes the high extinction ratio possible. On the other hand, the embedded SWG preferably affects the refractive index of the even mode in the coupling region and broadens the bandwidth of the splitter. As a result, the extinction ratio of 28.7 dB (24.8 dB) for TE (TM) is obtained, while the insertion loss is only 0.10 dB (0.11 dB) at the wavelength of 1550 nm. The extinction ratio is more than 10 dB in the wavelength range of 1450-1625 nm for TE and 1495-1610 nm for TM.

Faster-than-Nyquist non-orthogonal frequency-division multiplexing based on fractional Hartley transform: erratum

Yaojun Qiao, Ji Zhou, Zhanyu Yang, and Erkun Sun

Doc ID: 277757 Received 30 Sep 2016; Accepted 05 Oct 2016; Posted 10 Oct 2016  View: PDF

Abstract: This erratum is presented to correct the errors in our paper [Opt. Lett. 41, 4488-4491 (2016)].

High-efficiency self-focusing chip-fiber grating coupler for silicon nitride waveguides

Jian-Jun He, Yang Chen, Robert Halir, I. Molina-Fernández, and Pavel Cheben

Doc ID: 275303 Received 12 Sep 2016; Accepted 04 Oct 2016; Posted 05 Oct 2016  View: PDF

Abstract: Chip-fiber grating couplers have been widely used in silicon-on-insulator platform. In silicon nitride waveguides, the lower index contrast yields gratings with a weaker radiation strength and poor directionality, thereby limiting the coupling efficiency. Here we propose and design a self-focusing grating coupler in silicon nitride that employs both amplitude and phase apodizations to produce a Gaussian radiated beam with a converging wavefront which focuses on the optical fiber input aperture. Two-step etch stair-case grating teeth are used to achieve directionality as high as 93%. Full 3D finite-difference time-domain simulations show coupling from a 40 um x 40 um grating to an SMF-28 single mode fiber with a record calculated efficiency of 86% (0.66 dB loss) and a 3 dB bandwidth of 40 nm near 1550 nm wavelength.

Inverse-designed single-step-etched colorless 3 dB couplers based on RIE-lag-insensitive PhC-like subwavelength structures

Minming Zhang, Luluzi Lu, Deming Liu, Feiya Zhou, Dongyu Li, Mengfan Cheng, Lei Deng, Songnian Fu, and Jinsong Xia

Doc ID: 275485 Received 07 Sep 2016; Accepted 04 Oct 2016; Posted 05 Oct 2016  View: PDF

Abstract: Inverse-designed free-form nanophotonic structures have shown great potential in designing ultra-compact integrated photonic devices, but strict fabrication requirements may hinder their further applications. We here propose a photonic-crystal-like (PhC-like) subwavelength structure, which is insensitive to the lag effect, a most common fabrication error. A colorless 3 dB coupler employing such structure is designed, fabricated and characterized. With only one-step etching, the coupling region of our final device occupies a compact footprint of 2.72 μm × 2.72 μm. The simulated insertion loss of each output port is about 3.2 dB over 100 nm bandwidth around 1550 nm and the measured insertion losses of both ports are 3.35 dB in average over the observable 60 nm bandwidth with a near zero loss imbalance.

Digital holographic microscopy in label-free analysis of cultured cells response to photodynamic treatment

Nikolay Petrov, Andrei Belashov, Tatiana Belyaeva, Elena Kornilova, Anna Salova, Irina Semenova, Oleg Vasyutinskii, and Anna Zhikhoreva

Doc ID: 275727 Received 12 Sep 2016; Accepted 04 Oct 2016; Posted 04 Oct 2016  View: PDF

Abstract: A methodology is presented providing noninvasive monitoring and evaluation of the effect of photodynamic treatment on live cells \textit{in vitro}. Variations in morphological characteristics of cells in the course and after treatment are recorded by means of digital holographic microscopy. High-precision measurements of phase shift gained by probe radiation in HeLa and human endometrial mesenchymal stem cell cultures demonstrate for the first time changes of their volume occurred in response to treatment.

Direct Generation of Spatial Quadripartite Continuous Variable Entanglement in an Optical Parametric Oscillator

Jiangrui Gao, Kui Liu, Jun Guo, Chunxiao Cai, and junxiang zhang

Doc ID: 269347 Received 04 Jul 2016; Accepted 04 Oct 2016; Posted 04 Oct 2016  View: PDF

Abstract: Multipartite entanglement is used for quantum information applications such as building multipartite quantum communications. Generally, generation of multipartite entanglement is based on a complex beam-splitter network. Here, based on the spatial freedom of light, we experimentally demonstrated spatial quadripartite continuous variable entanglement among first order Hermite-Gaussian modes using a single type II optical parametric oscillator operating below threshold with a HG45o 01 pump beam. The entanglement can be scalable for larger numbers of spatial modes by changing the spatial profile of the pump beam. Also, spatial multipartite entanglement will be useful for future spatial multichannel quantum information applications.

Two-dimensional lattice solitons in polariton condensates with spin-orbit coupling

Yaroslav Kartashov and Dmitry Skryabin

Doc ID: 273970 Received 17 Aug 2016; Accepted 03 Oct 2016; Posted 04 Oct 2016  View: PDF

Abstract: We study properties of two-dimensional fundamental and vortex solitons in polariton condensates with spin-orbit coupling and Zeeman splitting evolving in square arrays of microcavity pillars. Due to repulsive character of excitonic nonlinearity such states are encountered in finite gaps in the spectrum of the periodic array. We show that spin-orbit coupling between two polarization components stemming from TE-TM energy splitting of the cavity photons lifts the degeneracy between vortex solitons with opposite topological charges and makes their density profiles and properties different for a fixed energy. In combination with Zeeman splitting in the external magnetic field this coupling leads to formation of four distinct families of vortex solitons with topological charges m=+-1, all of which can be stable. At the same time, only two stable families of fundamental gap solitons characterized by domination of different polari-zation components are encountered.

1.9-3.6 μm supercontinuum generation in a very short highly-nonlinear germanium fiber with a high mid-infrared power ratio

Jing Hou, Bin Zhang, Linyong Yang, Jinmei Yao, Ke Yin, and guangchen liu

Doc ID: 275018 Received 01 Sep 2016; Accepted 03 Oct 2016; Posted 04 Oct 2016  View: PDF

Abstract: In this letter, a broadband supercontinuum (SC) laser source which spanned from 1.9 to 3.6 μm with an all-fiber configuration was reported. This SC laser was obtained in concatenated single-mode thulium-doped fiber amplifier (TDFA) and 12 cm short highly-nonlinear germanium fiber. A 1.9-2.7 μm SC laser from the TDFA was spectrally-broadened continuously into the mid-infrared region (>3 μm) in the followed germanium fiber. When the repetition rate was 2 MHz, the obtained SC laser had a maximum output power of 6.12 W with an optical conversion efficiency of 15.3 % with respect to the TDFA pump power. The SC laser had a spectral bandwidth of 1506 nm ranging from 1944 to 3450 nm at -20 dB level. The SC power with wavelengths >3 μm was 2.9 W, corresponding to a high power ratio of 47.4 % in the mid-infrared region. Over 1 h stability test of this SC laser showed its outstanding power stability.

Mid-infrared supercontinuum generation in supercritical xenon-filled hollow-core negative curvature fibers

Md. Imran Hasan, Nail Akhmediev, and Wonkeun Chang

Doc ID: 274894 Received 02 Sep 2016; Accepted 03 Oct 2016; Posted 10 Oct 2016  View: PDF

Abstract: We present an investigation on the generation of supercontinuum in the mid-infrared spectral region. Namely, we study a silica-based anti-resonant hollow-core fiber which has a good guidance properties in the mid-infrared filled with supercritical xenon providing the necessary high nonlinearity. Our numerical study shows that by launching a 200 nJ pump of 100 fs centered at 3.7 μm, a supercontinuum that spans from 1.85 μm to 5.20 μm can be generated. Such sources are potentially highly useful for applications such as remote sensing of various molecules, medical imaging diagnosis and surgery.

Pseudo-random-bit-sequence phase modulation for reduced errors in a fiber optic gyroscope

Michel Digonnet and Jacob Chamoun

Doc ID: 268635 Received 20 Sep 2016; Accepted 30 Sep 2016; Posted 11 Oct 2016  View: PDF

Abstract: Low noise and drift in a laser-driven FOG are demonstrated by interrogating the sensor with a low-coherence laser. The laser coherence was reduced by broadening its optical spectrum using an external electro-optic phase modulator driven by either a sinusoidal or a pseudo-random bit sequence (PRBS) waveform. The noise reduction measured in a FOG driven by a modulated laser agrees with calculations based on the broadened laser spectrum. Using PRBS modulation the linewidth of a laser was broadened from 10 MHz to more than 10 GHz, leading to a measured FOG noise of only 0.00073 deg/√h and a drift of 0.0 deg/h. These are the lowest noise and drift demonstrated in a laser-driven FOG, and it is below the requirement for inertial navigation of aircraft.

Near-infrared photoresponse of femtosecond-laser processed Se-doped silicon n+-n photodiodes

Zhiming Wu, Lingyan Du, Rui Li, Fei Tang, and Yadong Jiang

Doc ID: 275429 Received 08 Sep 2016; Accepted 30 Sep 2016; Posted 04 Oct 2016  View: PDF

Abstract: Se-doped silicon was prepared using deposited Si-Se bilayer thin films followed by femtosecond-laser irradiation. n+-n photodiodes were fabricated from this material for the first time. The effects of annealing temperature and reverse bias voltage on the near-infrared responsivity were investigated. The photodiode exhibits optimal rectification and photoresponse at annealing temperature of 500 ℃. At 12 V bias, a responsivity of 2.41 A/W at 1064 nm is obtained. The linear increase at bias from 0 to 10V and faster-than-linear increase at bias from 10 to 12V for the responsivity are observed with the increase of the bias voltage. The results suggest that the gain mechanism is most likely to be photoconductive gain.

Printed Optics: Phantoms for Quantitative Deep Tissue Fluorescence Imaging

Kevin Webb, Brian Bentz, Anna Bowen, Dergan Lin, Daniel Ysselstein, Davin Huston, and Jean-Christophe Rochet

Doc ID: 273700 Received 11 Aug 2016; Accepted 28 Sep 2016; Posted 29 Sep 2016  View: PDF

Abstract: 3D printing allows complex or physiologically realistic phantoms, useful, for example, in developing biomedical imaging methods and for calibrating measured data. However, available 3D printing materials provide a limited range of static optical properties. We overcome this limitation with a new method using stereolithography that allows tuning of the printed phantom's optical properties to match that of target tissues, accomplished by printing a mixture of polystyrene microspheres and clear photopolymer resin. We show that Mie theory can be used to design the optical properties, and demonstrate the method by fabricating a mouse phantom and imaging it using fluorescence optical diffusion tomography (FODT).

High-order optical vortex generation in few-mode fiber via cascaded acoustically-driven vector mode conversion

Ting Mei, Wending Zhang, Ligang Huang, Keyan Wei, Peng Li, Biqiang Jiang, Dong Mao, Feng Gao, Guoquan Zhang, and Jianlin Zhao

Doc ID: 267872 Received 07 Jun 2016; Accepted 27 Sep 2016; Posted 03 Oct 2016  View: PDF

Abstract: We proposed a method to actualize high-order optical vortex generation in few-mode fiber via cascaded acoustically-driven vector mode conversion. Theoretical analysis showed that the vector mode conversion induced by the acoustically-induced fiber grating (AIFG) could only occur between two HE modes with adjacent azimuthal numbers. In the experiment conducted at 532 nm, two AIFGs were simultaneously induced in the same segment of fiber by an RF source containing two different frequency components. One AIFG was used to convert the left- and right-handed circular polarization fundamental modes to the ±1-order vortex modes, which were then further converted to the ±2-order vortex modes by the other AIFG. The topological charges of the vortex modes were verified using both coaxial and off-axial interference methods, showing typical signature patterns of spiral forms and forklike fringes, respectively.

Parametric instabilities in modulated fiber ring cavities

Matteo Conforti, François Copie, Arnaud Mussot, Alexandre Kudlinski, and Stefano Trillo

Doc ID: 269467 Received 30 Jun 2016; Accepted 26 Sep 2016; Posted 28 Sep 2016  View: PDF

Abstract: We investigate modulational instability in inhomogeneous passive cavities modeled by the Ikeda map. The cavity boundary conditions and the modulation of the fiber dispersion force the system to develop parametric instabilities, which lead to the generation of simple as well as period doubled temporal patterns. The analytical results obtained by means of Floquet theory are validated through numerical solution of the Ikeda map, and the limitation of the mean-field Lugiato-Lefever model are highlighted.

Experimental demonstration of bidirectional light transfer in adiabatic waveguide structures

Alexander Solntsev, Tong Liu, Andreas Boes, Christian Will, Arnan Mitchell, Dragomir Neshev, Andrey Sukhorukov, and Thach Nguyen

Doc ID: 273339 Received 08 Aug 2016; Accepted 25 Sep 2016; Posted 17 Oct 2016  View: PDF

Abstract: We propose and demonstrate a novel type of optical integrated structure consisting of three adiabatically coupled waveguides arranged in an N-shaped geometry. Unlike conventional adiabatic three-waveguide couplers mimicking the stimulated Raman adiabatic passage (STIRAP) process which utilize solely the counter-intuitive coupling and thus operate only in one direction, our structure achieves complete bidirectional light transfer between two waveguides through the counter-intuitive and intuitive coupling in either direction, over a wide wavelength range. Moreover, the light transfer through the intuitive coupling is more efficient and robust than through the counter-intuitive coupling.

Reducing noise in a Raman quantum memory

Philip Bustard, Duncan England, Khabat Heshami, Connor Kupchak, and Benjamin Sussman

Doc ID: 272636 Received 28 Jul 2016; Accepted 20 Sep 2016; Posted 05 Oct 2016  View: PDF

Abstract: Optical quantum memories are an important component of future optical, and hybrid, quantum technologies. Raman schemes are strong candidates for use with ultrashort optical pulses due to their broad bandwidth; however, the elimination of deleterious four-wave mixing noise from Raman memories is critical for practical applications. Here we demonstrate a quantum memory using the rotational states of hydrogen molecules at room temperature. Polarization selection rules prohibit four-wave mixing, allowing storage and retrieval of attenuated coherent states with mean photon number 0.9 and pulse duration 175fs. The 1/e memory lifetime is 85.5ps, demonstrating a time-bandwidth product of 480 in a memory that is well-suited to use with broadband heralded down-conversion and fiber-based photon sources.

Tunable MHz-bandwidth microwave photonic notch filter based on a silica microsphere cavity

Xinliang Zhang, Yang Liu, Yuan Yu, Shixing Yuan, xinbiao xu, and Lei Shi

Doc ID: 268415 Received 15 Jun 2016; Accepted 18 Sep 2016; Posted 19 Sep 2016  View: PDF

Abstract: We propose and experimentally demonstrate a tunable microwave photonic notch filter with MHz-order bandwidth, based on a silica microsphere cavity coupled by an optical microfiber. The silica microsphere with a quality factor of hundreds of millions, offers a full width at half maximum bandwidth down to the order of MHz in the transmission spectrum. Due to the coupling flexibility between the microcavity and the optical microfiber, the bandwidth and suppression ratio can be tuned and optimized to get a rejection ratio beyond 30 dB. The tunability of over 15 GHz is also achieved. As far as our best knowledge, this single-stopband microwave photonic filter has the narrowest-bandwidth filter that has been experimentally demonstrated. This microwave photonic notch filter shows distinct advantages of high selectivity, compactness, flexibility and low insertion loss. © 2015 Optical Society of America

Photonic Hilbert transformers based on laterally apodized integrated waveguide Bragg gratings on SOI wafer

Hamed Pishvai Bazargani, Maurizio Burla, Lukas Chrostowski, and Jose Azana

Doc ID: 274088 Received 19 Aug 2016; Accepted 10 Sep 2016; Posted 27 Sep 2016  View: PDF

Abstract: We experimentally demonstrate high-performance integer and fractional-order photonic Hilbert transformers (HTs) based on laterally apodized Bragg gratings in a silicon-on-insulator technology platform. The sub-millimeter-long gratings have been fabricated using single-etch electron beam lithography, and the resulting HT devices offer operation bandwidths approaching the THz range, with time-bandwidth products between 10 to 20.

Fiber-optic electron-spin-resonance thermometry of single laser-activated neurons

Aleksei Zheltikov, Alexandr Lanin, Ilya Fedotov, Yuliya Ermakova, Andrey Fedotov, Dmitry Sidorov-Biryukov, Philip Hemmer, and Vsevolod Belousov

Doc ID: 273389 Received 09 Aug 2016; Accepted 02 Sep 2016; Posted 02 Sep 2016  View: PDF

Abstract: Optically detected magnetic resonance in fiber-coupled nitrogen–vacancy (NV) centers of diamond is shown to enable in situ single-neuron thermometry on an all-optical platform for laser thermogenetics, which combines single-cell neurostimulation using heterologous thermosensitive cation channels with online fluorescence microscopy using fluorescent calcium-ion indicators. Laser-induced temperature variations read out from single neurons with the NV-diamond fiber sensor are shown to strongly correlate with the fluorescence of calcium-ion sensors, serving as online indicators of the inward Ca2+ current across the cell membrane of neurons expressing transient receptor potential (TRP) cation channels. Local laser heating above the TRP-channel activation threshold reproducibly evokes robust action potentials, visualized by calcium-ion-sensor-aided fluorescence imaging and detected as prominent characteristic waveforms in the time-resolved response of fluorescence Ca2+ sensors.

Noisy metamolecule: strong narrowing of fluorescence line: comment

Tomáš Chlouba, Martin Zonda, and Tomáš Novotný

Doc ID: 261063 Received 05 Apr 2016; Accepted 20 May 2016; Posted 01 Sep 2016  View: PDF

Abstract: We comment on the recent Letter by Andrianov {\em et al.} [Opt.~Lett.~40(15), 3536 (2015)], in which they study a strongly dissipative driven bosonic mode strongly coupled to a two-level system. The authors errorneously claim that the model cannot be studied by direct numerical methods and can be only tackled by the Quantum Monte Carlo simulations. We recalculate their quantities via sparse numerical solvers and find that their results for larger drives are incorrect, most likely due to insufficient Monte Carlo sampling in the presence of an emergent long time scale. These findings call for a corrected interpretation of the physical behavior responsible for narrowing of the fluorescence line as slow dichotomous switching between two quasiclassical photon field amplitudes.

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