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Accepted papers to appear in an upcoming issue

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Experimental demonstration of pulse multiplexing and beam combining of four fiber lasers by non-collinear frequency conversion in LBO crystal

Julijanas Zeludevicius, Kestutis Regelskis, and Gediminas Račiukaitis

Doc ID: 278362 Received 10 Oct 2016; Accepted 07 Dec 2016; Posted 07 Dec 2016  View: PDF

Abstract: In this work, we provide proof-of-concept experimental realization of pulse multiplexing and beam combining of four pulsed Yb-doped fiber lasers by non-collinear frequency up-conversion in LBO crystal. The overall conversion efficiency of 51% and up to 29 W average power in combined 532 nm beam was achieved. These results correspond to improvement by a factor of 2 compared to average power extracted from single fiber amplifier.

Influence of the photon orbital angular momentum on electric dipole transitions: negative experimental evidence

Anna Perona, Francesco Giammanco, Paolo Marsili, Fabio Conti, Francesco Fidecaro, Silvia Gozzini, and Alessandro Lucchesini

Doc ID: 279006 Received 08 Nov 2016; Accepted 07 Dec 2016; Posted 07 Dec 2016  View: PDF

Abstract: We describe an experiment of atomic spectroscopy devoted to ascertain whether the orbital angular momentum (OAM) of photons has the same property of interacting with atoms or molecules as it occurs for the spinangular momentum (SAM). In our experiment, Rubidium vapors are excited by means of a laser radiation with different combinations of OAM and SAM, particularly selected to inhibit or enhance the fluorescence according to the selection rules for the electric dipole transitions between the fundamental state and the first excited doublet. Our results show clearly that an electric dipole-type transition is insensitive to the OAM value.It provides an original validation of recent theoretical works.

Plasmonic non-concentric nano-rings array as unidirectional nano-optical conveyor belt actuated by polarization rotation

Guanghui Wang, Ho-Pui Ho, Xuping Zhang, min Jiang, Wenxiang Jiao, Zhoufeng Ying, Ningmu Zou, and Tianyu Sun

Doc ID: 279265 Received 14 Nov 2016; Accepted 07 Dec 2016; Posted 07 Dec 2016  View: PDF

Abstract: We report a nano-optical conveyor belt containing an array of gold plasmonic non-concentric nano-rings (PNNRs) for the realization of trapping and unidirectional transportation of nanoparticles through rotating the polarization of an excitation beam. The location of hot spots within an asymmetric plasmonic nanostructure is polarization dependent, thus making it possible to manipulate a trapped target by rotating the incident polarization state. In the case of PNNR, the two poles have highly unbalanced trap potential. This greatly enhances the chance of transferring trapped particles between adjacent PNNRs in a given direction through rotating the polarization. As confirmed by 3D FDTD analysis, an array of PNNRs forms a unidirectional nano-optical conveyor belt, which deliver target nano-particles or biomolecules over a long distance with nanometer accuracy. With the capacity to trap and to transfer, our design offers a versatile scheme for conducting mechanical sample manipulation in many on-chip optofluidic applications.

Low-loss Ge-rich Si0.2Ge0.8 waveguides for mid-infrared photonics

Joan Manel Ramirez, Vladyslav Vakarin, Clément Gilles, Jacopo Frigerio, Andrea Ballabio, Papichaya Chaisakul, Xavier LE ROUX, Carlos Alonso Ramos, GRégory Maisons, Laurent Vivien, Mathieu Carras, Giovanni Isella, and Delphine Marris-Morini

Doc ID: 280549 Received 09 Nov 2016; Accepted 06 Dec 2016; Posted 07 Dec 2016  View: PDF

Abstract: We demonstrate low-loss Ge-rich Si0.2Ge0.8 waveguides on Si1-xGex (x from 0 to 0.79) graded substrates operating in the mid-infrared wavelength range, at λ = 4.6 µm. Propagation losses as low as (1.5 ± 0.5) dB/cm and (2 ± 0.5) dB/cm were measured for the quasi-TE and quasi–TM polarizations, respectively. Total coupling loss (input/output) of only 10 dB was found for waveguide widths larger than 7 µm due to a good fiber-waveguide mode matching. Near-field optical mode profiles measured at the output waveguide facet allowed to inspect the optical mode and precisely measure the modal effective area of each waveguide providing a good correlation between experiments and simulations. These results put forward the potential of low-index-contrast Si1-xGex waveguides with high Ge concentration as fundamental blocks for mid-infrared photonic integrated circuits.

Semiconductor laser linewidth reduction by six orders of magnitude via delayed optical feedback

Daniel Brunner, Raimon Luna, Adrià Delhom I Latorre, Xavier Porte, and Ingo Fischer

Doc ID: 278335 Received 11 Oct 2016; Accepted 06 Dec 2016; Posted 06 Dec 2016  View: PDF

Abstract: We demonstrate a coherence increase by six orders of magnitude of a standard quantum well semiconductor laser. Using a simple, optical-fiber based feedback scheme we stabilize the laser in a high-gain mode of a long external cavity. In a modified self-heterodyne measurement, we mix the high-gain mode with a strongly suppressed side mode and obtain an interference linewidth of only 12.6 Hz, corresponding to a decoherence of (3.1$\pm$2.9) Hz. In an independent characterization using an etalon, we deduce an upper limit of 300 Hz for the laser linewidth. The laser stably resides in this mode for tens of seconds. Our results agree with theoretical predictions.

Dual-Focus coherent anti-Stokes Raman Scattering (CARS) microscopy using a compact two-beam fiber laser source

Juergen Popp, Fisseha-Bekele Legesse, Tobias Meyer, Sandro Heuke, Thomas Gottschall, Jens Limpert, Andreas Tünnermann, Michael Schmitt, and Torbjoern Pascher

Doc ID: 278345 Received 18 Oct 2016; Accepted 06 Dec 2016; Posted 07 Dec 2016  View: PDF

Abstract: CARS) microscopy using a compact two-beam fiber laser sourceWe developed a dual focus coherent anti-Stokes Raman scattering (CARS) microscope based on a dual output, compact fiber laser source. The underlying concepts of time multiplexed, two-beam scanning and demultiplexed detection that we already employed for second harmonic generation (SHG) are here naturally extended for CARS microscopy. The layout of a robust, all-fiber laser source was re-configured to provide two outputs, each containing the two colours necessary for the CARS process. The utilization of the design for simultaneously imaging two laterally or axially separated fields of view, and thus inherently speeding up the image acquisition process, is demonstrated on human artery tissue samples.

AM-to-PM Conversion in a Resonant Microwave Optical Rectification Detector

Brian Kolner and Lanbing Kang

Doc ID: 276469 Received 26 Sep 2016; Accepted 05 Dec 2016; Posted 07 Dec 2016  View: PDF

Abstract: A LiNbO₃-loaded microwave cavity pumped with weakly AM-modulated 30 fs optical pulses was used as a platform to investigate AM-to-PM conversion in the optical rectification process. Theoretical treatment of AM-to-PM conversion (i.e. peak induced electrical phase deviation β_i due to optical power modulation with index m) suggests the dominant mechanism is self group-velocity modulation (SGM) due to χ^(3) and cascaded χ^(2) processes with a value of δ=β_i/m=-151 dB, linearly dependent on optical power at intensities of 6×10^{10} W/m² in a 40 mm long LiNbO₃ crystal. This is in stark contrast to p-i-n photodiodes which can exhibit AM-to-PM conversion gain δ>0 dB. In this experiment we measured values of δ for a resonant optical rectification detector using typical modelocked Ti:sapphire laserpulses (100 MHz, 30 fs, P_avg approximately = 100$ mW) and found aninstrumentation-limited lower bound of δ approximately = -43.5$ dB,independent of optical power.

Generation of narrowband, high-intensity, carrier-envelope phase stable pulses tunable between 4 and 18 THz

Michael Först, Bialong Liu, Hubertus Bromberger, Thomas Gebert, Andrea Cartella, and Andrea Cavalleri

Doc ID: 279310 Received 24 Oct 2016; Accepted 05 Dec 2016; Posted 06 Dec 2016  View: PDF

Abstract: We report on the generation of high-energy (1.9 µJ) far- infrared pulses tunable between 4 and 18 THz frequency. Emphasis is placed on tunability and on minimizing the bandwidth of these pulses to less than 1 THz, as achieved by difference-frequency mixing of two linearly chirped near-infrared pulses in the organic nonlinear crystal DSTMS. As the two near-infrared pulses are derived from amplification of the same white light continuum their carrier envelope phase fluctuations are mutually correlated, and hence the difference-frequency THz field exhibits absolute phase stability. This source opens up new possibilities for the control of condensed matter and chemical systems by selective excitation of low-energy modes in a frequency range that has to date been difficult to access.

High Peak Power Cavity Dumping Semiconductor Lasers

Joshua Myers, Robert Bedford, Gary Cook, and Christopher Kokoczka

Doc ID: 277645 Received 27 Sep 2016; Accepted 05 Dec 2016; Posted 05 Dec 2016  View: PDF

Abstract: We report on the development of a nanosecond pulsed kW-class optically-pumped semiconductor laser suitable for applications such as incoherent laser radar, nonlinear optics, and materials processing. Using an intracavity Pockels cell to cavity-dump VECSELs, we are able to access large pulse energies by storing energy in the optical cavity rather than in the gain medium. We demonstrate peak powers >1 kW and 3 μJ pulses, show the pulse length is equivalent to the photon round-trip time, and that the wavelength can be tuned within the gain bandwidth of the semiconductor gain.

Quantized pulse separations of phase-locked soliton molecules in a dispersion-managed mode-locked Tm fiber laser at 2-μm

Changxi Yang, Pan Wang, and Xiaosheng Xiao

Doc ID: 278191 Received 11 Oct 2016; Accepted 04 Dec 2016; Posted 05 Dec 2016  View: PDF

Abstract: We report, for the first time to our knowledge, the discovery of quantized pulse separations between phase-locked soliton pairs in a thulium-doped fiber laser at the wavelength range of 2-μm. The soliton pairs are formed by the nonlinear binding interaction between the solitons and dispersive waves, and the two-lowest order Kelly sidebands drive the interaction in these soliton pairs and fix the pulse separations of the soliton pairs to a discrete set of values. Our experimental observations are well confirmed by numerical simulations. Meanwhile, soliton molecules composed of three or more solitons with various self-organized structures are also obtained.

ZnO-Nanowires enabled light funneling effect for antireflection and light convergence applications

Bikash Choudhury, Pankaj Sahoo, Joby Joseph, and Srinivasan Anand

Doc ID: 279877 Received 02 Nov 2016; Accepted 04 Dec 2016; Posted 05 Dec 2016  View: PDF

Abstract: We present a new light trapping technique to reduce reflection loss as well as for light focusing at submicron scales for solar cell and image sensing applications. We have fabricated hexagonal arrays of ZnO-funnel like structures on Si substrate by patterned growth of ZnO nanowires in a hydrothermal growth process. Funnels are optimized, so that the effective refractive index along vertical direction decreases gradually from Si surface to the top of funnel to reduce Fresnel reflection at device-air interface. Finite difference time domain (FDTD) simulation is used, for optimization of the minimum reflectivity and, to analyze optical properties like angle dependency, polarization dependency and funneling effect. The structures function similar to GRIN lens in light trapping and convergence. Optimized structure reduces average reflectivity close to 3% in the wavelength range of 300-1200nm with possibility of confining incident light to few hundreds of nanometers.

V-band Gapless OFDM RoF System with Power Detector Down-conversion and Novel Volterra Nonlinear Filtering

Chun-Ting Lin, Shou-Chih Chiang, che-hao Li, Hou-Tzu Huang, Chi-Hsiang Lin, and BO-JIUN Lin

Doc ID: 279974 Received 02 Nov 2016; Accepted 03 Dec 2016; Posted 05 Dec 2016  View: PDF

Abstract: This paper presents a V-band gapless OFDM RoF system at 60 GHz employing power detector to support vector signal down-conversion. Additional RF tone is generated and transmitted from central station (CS) to replace the local oscillator (LO) at wireless receiver for power detector down-conversion. To enhance spectrum efficiency, the gap between OFDM signal and RF tone is not needed. However, the down-converted signal will suffer signal-to-signal-interference (SSBI). In this paper, we propose and successfully employ a novel Volterra nonlinear compensation to mitigate SSBI, resulting in 22% data rate improvement with bit-loading algorithm.

Improving the imaging speed of 1064 nm dispersive Raman microscopy with multifocal patterned detection

James Chan and Maria Navas Moreno

Doc ID: 278303 Received 10 Oct 2016; Accepted 03 Dec 2016; Posted 05 Dec 2016  View: PDF

Abstract: We demonstrate the compatibility of a Hadamard coded multifocal array approach with a 1064 nm dispersive Raman microscope for improving imaging speed. The system uses a galvomirror to generate a one-dimensional (1-D) multifocal array at the sample and the Raman signals from the multiple foci are simultaneously detected by an InGaAs linear detector array. The superimposed spectra are deconvolved to retrieve the individual spectra at each focus. Using a silicon wafer as a test sample, we demonstrate that the method is ideal for the high noise detection conditions encountered when using 1064 nm excitation, InGaAs detectors, and high readout rates. An improvement in imaging speed by as much as 14 times is achieved with this multifocal method.

Octave-spanning coherent perfect absorption in a thin silicon film

Ayman Abouraddy, Lorelle Pye, Massimo Villinger, Soroush Shabahang, Walker Larson, and Lane Martin

Doc ID: 281422 Received 24 Nov 2016; Accepted 02 Dec 2016; Posted 02 Dec 2016  View: PDF

Abstract: Though optical absorption is an intrinsic materials property, it can nevertheless be manipulated through structural modification. Coherent perfect absorption increases absorption to 100\% interferometrically, but is typically realized only over narrow bandwidths using two laser beams with fixed phase relationship. We show that engineering a thin film’s photonic environment severs the link between the \textit{effective} absorption of the film and its \textit{intrinsic} absorption while eliminating, in principle, bandwidth restrictions. Employing thin aperiodic dielectric mirrors, we demonstrate coherent perfect absorption in a 2-micron-thick film of polycrystalline silicon using a single \textit{incoherent} beam of light at all the resonances across a spectrally flat, octave-spanning near-infrared spectrum, $\approx\!800\!-\!1600$~nm. Critically, these mirrors have wavelength-dependent reflectivity devised to counterbalance the decline in silicon’s intrinsic absorption at long wavelengths.

Anomalous nonradiative decay in Dy-doped glasses and crystals

Richard Quimby and Mohammed Saad

Doc ID: 279471 Received 27 Oct 2016; Accepted 02 Dec 2016; Posted 05 Dec 2016  View: PDF

Abstract: Nonradiative relaxation in Dy-doped fluoroindate glass is measured and characterized in terms of the well-known exponential energy gap law. It is found that although three low-lying Dy transitions fit well with an exponential dependence on energy gap, the overall magnitude of the Dy decay rate is an order of magnitude higher than that of other rare earth ions. It is also found that the nonradiative decay rates in InF₃ glass are comparable to those in ZrF₄ glass, contrary to expectations based on maximum phonon energy. These unexpected results have important implications for a potential 4 um Dy:InF₃ fiber laser.

High Speed Resonantly Enhanced Silicon Photonics Modulator with Large Operating Temperature Range

Sebastian Romero-Garcia, M. Saeed Sharif Azadeh, Juliana Mueller, Alvaro Moscoso-Mártir, Bin Shen, Florian Merget, and Jeremy Witzens

Doc ID: 278364 Received 12 Oct 2016; Accepted 02 Dec 2016; Posted 02 Dec 2016  View: PDF

Abstract: We present a novel resonant MZM whose arms are each loaded with five identical resonators. Size and power consumption are aggressively reduced compared to conventional modulators based on linear phase shifters. At the same time, a large optical bandwidth of 3.8 nm is maintained. We experimentally demonstrate open eye diagrams at 30 Gbps with a signal Q-factor remaining within a factor 2 of its peak value in an operational temperature range spanning 55 °C.

Spatial-division multiplexed Brillouin distributed sensing based on heterogeneous multicore fiber

Ming Tang, Zhiyong Zhao, Yunli Dang, Li Borui, Lin Gan, Fu Songnian, Huifeng Wei, Tong Weijun, Ping Shum, and Deming Liu

Doc ID: 280331 Received 08 Nov 2016; Accepted 02 Dec 2016; Posted 07 Dec 2016  View: PDF

Abstract: We have experimentally investigated spatial-division multiplexed (SDM) Brillouin optical time-domain analysis (BOTDA) in heterogeneous multicore fiber (MCF), whose central core and six outer cores are made from different preforms, showing ~70 MHz Brillouin frequency shift (BFS) difference between them. It reveals that the heterogeneous central core and outer cores have different temperature sensitivities, but their strain sensitivities are almost the same. By making use of the distinct temperature coefficients of these two kinds of cores, simultaneous and discriminative temperature and strain measurements are achieved. The bending induced Brillouin gain spectrum (BGS) broadening issue in off-center cores has been clarified, and a solution has been proposed to eliminate the uncertainty caused by bending induced BFS shift when performing the discrimination, by averaging the BFS variations of two symmetrical outer cores. We show new perspective for discriminative measurement in Brillouin distributed sensors based on SDM system configuration.

A simple approach to high-fidelity tunable narrow-band pulse generation

Vladislav Yakovlev, Charles Ballmann, and Georgi Petrov

Doc ID: 278542 Received 17 Oct 2016; Accepted 01 Dec 2016; Posted 02 Dec 2016  View: PDF

Abstract: Tunable narrow-band short-pulse coherent emission can be generated by optical parametric amplification of seeded continuous wave (CW) laser. However, the residual CW pedestal can affect the accuracy of optical measurements and the exact interpretation of experimental data. Wedemonstrate a simple approach to remove the residual CW seed in a frequency tunable, seeded parametric amplification setup in the nanosecond regime by adding an additional parametric amplification stage which is seeded by anidler wave from the first stage. We validate this method using pump-probe experiments in atomic vapors.

Spatial mode multiplexing/demultiplexing by Gouy phase interferometry

Jesús Liñares, Xesús Prieto-Blanco, Carlos Montero-Orille, and Vicente Moreno

Doc ID: 279000 Received 19 Oct 2016; Accepted 01 Dec 2016; Posted 02 Dec 2016  View: PDF

Abstract: We present a theoretical study about spatial mode multiplexing/demultiplexing (mux/demux) without theoretical losses by means of interferometry with selective control of the Gouy phase of optical beams, that is, Gouy phase interferometry (GPI). Different Gouy phase values can be obtained by inserting appropri- ate optical systems at each arm of an interferometer. Thus, spatial mode mux/demux operations, of strate- gic interest in optical communications with few-mode optical fibers, are implemented by means of constructive interference and regardless the parity and separability of the optical beams. Consequently, unachievable mux/demux by interferometry based on image in- version methods becomes possible with GPI. This kind of operations can also be interesting for optical sensors, optical metrology, image processing and so on.

A reconfigurable microwave photonic mixer with minimized path separation and large suppression of mixing spurs

Shilong Pan and Zhenzhou Tang

Doc ID: 278378 Received 10 Oct 2016; Accepted 01 Dec 2016; Posted 01 Dec 2016  View: PDF

Abstract: A compact reconfigurable photonic microwave mixer is proposed and demonstrated based on a dual-polarization Mach-Zehnder modulator (DPol-MZM) and an optical 90-degree hybrid. By simply changing the photodetection schemes, single-ended, double-balanced, I/Q and image-reject mixing can be implemented. Thanks to the sidebands selection by an optical filter, unwanted mixing spurs are highly suppressed. In addition, the system is insensitive to environmental vibration because the optical path separation is minimized. An experiment is carried out. Reconfigurable mixing functionalities with very small phase dithering are verified. The mixing spurs are suppressed by more than 30 dB and the image-reject ratio for image-reject mixing is about 40 dB. The proposed mixer features simple configuration and stable operation, which can find applications in broadband and multifunctional microwave photonic systems.

Fiber ring resonator with nanofiber section for chiral cavity quantum electrodynamics and multimode strong coupling

Juergen Volz, Philipp Schneeweiss, Arno Rauschenbeutel, Sophie Zeiger, and Thomas Hoinkes

Doc ID: 280387 Received 09 Nov 2016; Accepted 01 Dec 2016; Posted 01 Dec 2016  View: PDF

Abstract: We experimentally realize an optical fiber ring resonator that includes a tapered section with subwavelength-diameter waist. In this section, the guided light exhibits a significant evanescent field which allows for efficient interfacing with optical emitters. A commercial tunable fiber beam splitter provides simple and robust coupling to the resonator. Key parameters of the resonator such as its out-coupling rate, free spectral range, and birefringence can be adjusted. Thanks to the low taper- and coupling-losses, the resonator exhibits an unloaded finesse of F=75±1, sufficient for reaching the regime of strong coupling for emitters placed in the evanescent field. The system is ideally suited for trapping ensembles of laser-cooled atoms along the nanofiber section. Based on measured parameters, we estimate that the system can serve as a platform for optical multimode strong coupling experiments. Finally, we discuss the possibilities of using the resonator for applications based on chiral quantum optics.

Synthesis of the Einstein-Podolsky-Rosen entanglement in a sequence of two single-mode squeezers

Alexander Ulanov, Ilya Fedorov, Alexander Lvovsky, and Yury Kurochkin

Doc ID: 280015 Received 02 Nov 2016; Accepted 01 Dec 2016; Posted 06 Dec 2016  View: PDF

Abstract: We propose and implement a new scheme of generating optical Einstein-Podolsky-Rosen entangled state. Parametric down-conversion in two nonlinear crystals, positioned back-to-back in the waist of a pump beam, produces single-mode squeezed vacuum states in orthogonal polarization modes; a subsequent beam splitting entangles them and generates the Einstein-Podolsky-Rosen state. The technique takes advantage of the strong nonlinearity associated with type-0 phasematching configuration while at the same time eliminating the need for actively stabilizing the optical phase between the two single-mode squeezers. We demonstrate our method, preparing a 1.4 dB two-mode squeezed state and characterizing it via two-mode homodyne tomography.

Mid Wave Infrared Narrow Bandwidth Guided Mode Resonance Notch Filter

Dan Wasserman, Yujun Zhong, Zipporah Goldenfeld, Will Streyer, Lan Yu, Neil Murphy, leland Nordin, and Kun Li

Doc ID: 279909 Received 03 Nov 2016; Accepted 30 Nov 2016; Posted 06 Dec 2016  View: PDF

Abstract: We have designed, fabricated and characterized a guided mode resonance notch filter operating in the technologically vital mid-wave infrared region of the electromagnetic spectrum. The filter provides a bandstop at λ≈4.1μm, with a 12dB extinction on resonance. In addition, we demonstrate a high transmission background (>80%), less than 6% transmission on resonance, and an ultra-narrow bandwidth transmission notch (10 cm-1). Our filter is optically characterized using angle- and polarization- dependent Fourier transform infrared spectroscopy, and simulated using rigorous coupled-wave analysis (RCWA) with excellent agreement between simulations and our experimental results. Using our RCWA simulations, we are able to identify the optical modes associated with the transmission dips of our filter. The presented structure offers a potential route towards narrow-band laser filters in the mid-wave infrared.

Rabi oscillations produced by adiabatic pulse due to initial atomic coherence

Anatoly Svidzinsky, Hichem Eleuch, and Marlan Scully

Doc ID: 281071 Received 17 Nov 2016; Accepted 30 Nov 2016; Posted 02 Dec 2016  View: PDF

Abstract: If electromagnetic pulse is detuned from atomic transition frequency by amount \Delta >1/T, where T is the turn on time of the pulse, then atomic population adiabatically follows the pulse intensity without causing Rabi oscillations. Here we show that if initially the atom has nonzero coherence then the adiabatic pulse yields Rabi oscillations of atomic population \rho_{aa}(t) and obtain analytical solutions for \rho_{aa}(t). Our findings can be useful for achieving generation of coherent light in the backward direction in the QASER scheme in which modulation of the coupling between light and atoms is produced by Rabi oscillations. Initial coherence can be created by sending a short resonant pulse into the medium followed by a long adiabatic pulse which leads to the light amplification in the backward direction.

Multifiber Optical coherence tomography (MFOCT) for speckle reduction

Dongyao Cui, EN BO, Yuemei Luo, Xinyu Liu, xianghong wang, Si Chen, Xiaojun Yu, shi chen, Ping Shum, and Linbo Liu

Doc ID: 279096 Received 26 Oct 2016; Accepted 29 Nov 2016; Posted 05 Dec 2016  View: PDF

Abstract: We report an integrated fiber optic design to implement multichannel spectral-domain optical coherence tomography, which enables angular compounding for speckle reduction. A multi-facet fiber array delivers three light beams to the sample with different incident angles. Back-reflective / back-scattered signals from these channels were simultaneously detected by a three-channel spectrometer. The axial and lateral resolution were measured to be ~3 µm and ~7 µm respectively in air with ~100 dB sensitivity. We conducted ex vivo experiments on rat esophagus to demonstrate a contrast to noise improvement of 1.58.

Effect of pumping delay on the modulation bandwidth in double tunneling-injection quantum dot lasers

Levon Asryan

Doc ID: 279019 Received 19 Oct 2016; Accepted 29 Nov 2016; Posted 02 Dec 2016  View: PDF

Abstract: The modulation bandwidth of double tunneling-injection (DTI) quantum dot (QD) lasers is studied taking into account noninstantaneous pumping of QDs. In this advanced type of semiconductor lasers, carriers are first captured from the bulk waveguide region into two-dimensional regions (quantum wells – QWs) and then they tunnel from the QWs into zero-dimensional regions (QDs). The two processes are noninstantaneous and thus could delay the delivery of carriers to the QDs. Here, the modulation bandwidth of DTI QD lasers is calculated as a function of two characteristic times (capture time from the waveguide region into the QW and tunneling time from the QW into the QD-ensemble) and shown to increase as either of these times is reduced. The capture and tunneling times of 1 and 0.1 ps, respectively, are shown to characterize fast capture and tunneling processes — as the capture and tunneling times are brought below 1 and 0.1 ps, the bandwidth remains almost unchanged and close to its upper limit.

Random sources for rotating spectral densities

Olga Korotkova and Zhangrong Mei

Doc ID: 278773 Received 17 Oct 2016; Accepted 29 Nov 2016; Posted 02 Dec 2016  View: PDF

Abstract: The far-field mode structure of a wide-sense stationary Schell-like source with arbitrary coherence state and a twist factor is determined. This suggests a convenient practical method for modeling novel classes of twisted partially coherent beam-like fields. The first example discusses previously introduced twisted anisotropic Gaussian-Schell model source, and verifies the feasibility of this method. As a second example, we introduce a new type of twisted partially coherent beam in which a radiated flat-top average intensity pattern remains invariant in shape (but not size) while twists around the axis upon propagation.

Singlemode Raman lasing at 954 nm in a graded-index fiber directly pumped by a multimode laser diode

Sergey Babin, Ekaterina Zlobina, Sergey Kablukov, Alexey Wolf, and Alexandr Dostovalov

Doc ID: 279738 Received 31 Oct 2016; Accepted 29 Nov 2016; Posted 29 Nov 2016  View: PDF

Abstract: High beam quality and narrow spectrum have been obtained in a Raman fiber laser based on a 1.1-km-long graded-index fiber directly pumped by a multimode 915-nm laser diode. Single transverse mode generation at 954 nm with M2≈1.2 and Δλ≈0.4 nm at output power above 10 W is enabled by cavity mirror made of special fiber Bragg grating inscribed by femtosecond technique in central part of the graded-index fiber core.

Active Flat Optics Using a Guided Mode Resonance

Mark Brongersma and Soo Jin Kim

Doc ID: 280143 Received 04 Nov 2016; Accepted 29 Nov 2016; Posted 29 Nov 2016  View: PDF

Abstract: Dynamically-controlled flat optics relies on achieving active and effective control over light-matter interaction in ultrathin layers. A variety of metasurface designs have achieved efficient amplitude and phase modulation. Particularly noteworthy progress has been made with the incorporation of newly emerging electro-optical materials into such metasurfaces, including graphene, phase change materials and transparent conductive oxides. In this letter, we demonstrate dynamic light-matter interaction in a silicon-based subwavelength grating that supports a guided mode resonance. By overcoating the grating with indium tin oxide as an electrically tunable material, its reflectance can be tuned from four to eighty six percent. Guided mode resonances naturally afford higher optical quality factors than the optical antennas used in the construction of metasurfaces. As such, they facilitate more effective control over the flow of light within the same layer thickness.

Saturation compensated fluorescence lifetime imaging microscopy

Yide Zhang, Genevieve Vigil, Lina Cao, Aamir Khan, David Benirschke, Tahsin Ahmed, Patrick Fay, and Scott Howard

Doc ID: 279389 Received 26 Oct 2016; Accepted 29 Nov 2016; Posted 30 Nov 2016  View: PDF

Abstract: Fluorophore saturation is the key factor limiting the speed and excitation range of fluorescence lifetime imaging microscopy (FLIM). For example, fluorophore saturation causes incorrect lifetime measurements when using conventional frequency domain FLIM at high excitation powers. In this Letter, we present an analytical theoretical description of this error and present a method for compensating for this error in order to extract correct lifetime measurements in the limit of fluorophore saturation. We perform a series of simulations and experiments to validate our methods. The simulations and experiments show 13.2x and 2.6x increase in excitation range, respectively. The presented method is based on algorithms that can be easily applied to existing FLIM setups.

High-extinction ratio integrated photonic filters for silicon quantum photonics

Mateusz Piekarek, Damien Bonneau, Shigehito Miki, Taro Yamashita, Mikio Fujiwara, Masahide Sasaki, H Terai, Michael Tanner, Robert Hadfield, Chandra Natarajan, Jeremy O'Brien, and Mark Thompson

Doc ID: 269910 Received 06 Oct 2016; Accepted 29 Nov 2016; Posted 01 Dec 2016  View: PDF

Abstract: We present the generation of quantum-correlated photon pairs and subsequent pump rejection across two silicon-on-insulator photonic integrated circuits. Incoherently cascaded lattice filters are used to provide over 100 dB pass-band to stop-band contrast with no additional external filtering. Photon pairs generated in a microring resonator are successfully separated from the input pump, confirmed by a temporal correlations measurements.

Improving the estimation of flow speed for laser speckle imaging with single exposure time

Pengcheng Li, yang wang, Jinling Lu, Qin Huang, chen xiao, Dong Wen, and ming chen

Doc ID: 272960 Received 02 Aug 2016; Accepted 28 Nov 2016; Posted 01 Dec 2016  View: PDF

Abstract: Laser speckle contrast imaging (LSCI) is a full-field imaging technique for measuring blood flow by mapping the speckle contrast with high spatial and temporal resolution. However, the statically scattered light from stationary tissues seriously degrades the accuracy of flow speed estimation. In this letter, we present a simple calibration approach to calculate the proportions of dynamically scattered light and correct the effect of static scattering with single exposure time. Both the phantom and animal experimental results suggest that this calibration approach has the ability to improve the estimation of relative blood flow in the presence of static scattering.

Geometric phase shaping of terahertz vortex beams

Emmanuel Abraham, Amalya Minasyan, Clément Trovato, Jérôme Degert, Eric FREYSZ, and Etienne Brasselet

Doc ID: 279047 Received 19 Oct 2016; Accepted 28 Nov 2016; Posted 02 Dec 2016  View: PDF

Abstract: We propose topological beam shaping strategy of terahertz (THz) beams using geometric phase elements made of space variant birefringent slabs. Quasi-monochromatic THz vortex beams with unit topological charge are produced and characterized both in amplitude and phase from reconstructed real-time two-dimensional imaging of the electric field. Nonseparable superpositions of such vortex beams are also obtained and characterized by two-dimensional polarimetric analysis. These results emphasize the versatility of the spin-orbit electromagnetic toolbox to prepare on-demand structured light endowed with polarization-controlled orbital angular momentum content in the THz domain, which should find many uses in future THz technologies.

Increase in laser-induced damage threshold of sapphire windows by means of direct dielectric barrier discharge plasma treatment

Christoph Gerhard, Daniel Tasche, Norbert Munser, and Helene Dyck

Doc ID: 279189 Received 20 Oct 2016; Accepted 28 Nov 2016; Posted 29 Nov 2016  View: PDF

Abstract: In this Letter we present a novel approach for increasing the laser-induced damage threshold (LIDT) of sapphire windows. It is shown that after direct dielectric barrier discharge plasma treatment at atmospheric pressure for 90 seconds the LIDT is increased by a factor of 1.7 with respect to untreated samples. Several possible underlying mechanisms are introduced. First, organic contaminants and residues from polishing agents were removed by the plasma as ascertained by XPS measurements. Second, it is shown by AFM analysis that the sample surfaces were smoothed.

Compressive Sensing Resonator Spectroscopy

Yaniv oiknine, Yitzhak August, Dan Blumberg, and Adrian Stern

Doc ID: 278356 Received 10 Oct 2016; Accepted 28 Nov 2016; Posted 29 Nov 2016  View: PDF

Abstract: We present a new fast compressive spectroscopic technique based on the resonance spectrometric mechanism. This technique uses an appropriately designed Fabry-Perot resonator and a photo-sensor in order to acquire different multiplexed spectral modulations, from which the original signal is reconstructed using a compressive sensing reconstruction algorithm. We present experimental results that demonstrate the acquisition of hundreds of spectral bands with a compression ratio of about 1:13.

Nonlinear imaging in photonic lattices

Nikolaos Efremidis and Mihalis Barkas

Doc ID: 278491 Received 11 Oct 2016; Accepted 28 Nov 2016; Posted 29 Nov 2016  View: PDF

Abstract: We show that nonlinear imaging is possible in periodic waveguide configurations provided that we use two different segments of nonlinear media with opposite signs of the Kerr nonlinearity with, in general, no other restriction about their magnitudes. The second medium is used to implement effective ``reverse propagation'. A main ingredient in achieving nonlinear imaging is the control of the sign and the amplitude of the coupling coefficient. We numerically test our results in one and two dimensional square arrangement of waveguides.

414 W near-diffration-limited all-fiberized single-frequency polarization-maintained fiber amplifier

Long Huang, Wu Hanshuo, Ruixian Li, Lei Li, Pengfei Ma, Xiaolin Wang, Jinyong Leng, and Pu Zhou

Doc ID: 278522 Received 12 Oct 2016; Accepted 28 Nov 2016; Posted 29 Nov 2016  View: PDF

Abstract: A high power 1064 nm single-frequency polarization-maintained fiber amplifier based on all-fiber master oscillator power amplifier configuration is demonstrated. To mitigate the stimulated Brillouin scattering (SBS) and the mode instability (MI) effect, polarization-maintained Yb-doped fiber with high dopant concentration and 25m core diameter is adopted in the main amplifier stage, in addition, step-distributed longitudinal strain is imposed on the active fiber to broaden its effective SBS gain spectrum and further increase the SBS threshold. As a result, a pump-limited 414 W single-frequency fiber laser is obtained without signs of SBS and MI. Experimental results show that the SBS threshold is increased by at least two times. The slope efficiency of the main amplifier is about 80 %. The polarization degree is higher than 98 % at all the power levels. The beam quality is measured with a M2 of 1.34. To the best of our knowledge, this is the highest output power of single-frequency polarization-maintained fiber amplifier based on all-fiber structure up to now.

Large-scale silicon nitride nanophotonic phased arrays at infrared and visible wavelengths

Christopher Poulton, Michael Watts, Matthew Byrd, Manan Raval, Zhan Su, Erman Timurdogan, Nanxi Li, Diedrik Vermeulen, and Douglas Coolbaugh

Doc ID: 275446 Received 17 Oct 2016; Accepted 27 Nov 2016; Posted 28 Nov 2016  View: PDF

Abstract: We demonstrate passive large-scale nanophotonic phased arrays in a CMOS compatible silicon photonic platform. Silicon nitride is utilized to allow for higher input power and lower phase noise compared to a silicon-based distribution network. A phased array at an infrared wavelength of 1550nm is demonstrated with an ultra-large aperture size of 4×4mm2, achieving a record-small and near diffraction limited spot size of 0.021°×0.021° with a side lobe suppression of 10dB. A main beam power of 400mW is observed. Using the same silicon nitride platform and phased array architecture, we also demonstrate the first large-aperture visible nanophotonic phased array at 635nm with an aperture size of 0.5×0.5mm2 and a spot size of 0.064°×0.074°.

A plasmonic wavelength splitter based on a sub-wavelength metal–insulator–metal periodic rectangle wrinkle waveguide with a graded grating coupler

Yue Yu, Xiaoxu Deng, Jiangnan Si, Yaying Ning, and Minghai Sun

Doc ID: 272216 Received 02 Sep 2016; Accepted 27 Nov 2016; Posted 30 Nov 2016  View: PDF

Abstract: A plasmonic wavelength splitter based on a sub-wavelength metal-insulator-metal (MIM) periodic rectangle wrinkle waveguide with a graded grating coupler is theoretical analysis and experimentally demonstrated. The SPPs, excited in the metal grating with wavelength–selection, are deflected by the graded difference according to the aplanatic parametric principle. The wave vector of the deflected SPPs meet the phase-matching condition and couple into the periodic rectangle wrinkle waveguide with a plasmonic band gap. The characteristic of the plasmonic wavelength splitter is simulated by FDTD, which agrees well with the theoretical analysis. By electron beam lithography and iron beam etches process, the plasmonic wavelength splitter was fabricated. The SPPs excited by incident 650 nm and 832 nm were successfully split and guided to opposite directions of the MIM waveguide with extinction ratios of 27.5dB and 32.7dB, respectively, which was observed under an optical microscope using a CCD camera. The proposed wavelength splitter is simple fabricated, and has a large coupling aperture by utilizing the graded grating coupler.

Visible light emission from a silica microbottle resonator by second and third harmonic generation

Motoki Asano, Rikizo Ikuta, Nobuyuki Imoto, Takashi Yamamoto, Sahin Sahin Ozdemir, and Shoichi Komori

Doc ID: 277847 Received 30 Sep 2016; Accepted 25 Nov 2016; Posted 28 Nov 2016  View: PDF

Abstract: We report the first observation of nonlinear harmonic generation and sum frequency generation (SFG) coupled with stimulated Raman scattering (SRS) via the second-order (χ²) and the third-order (χ³) nonlinearities in a silica microbottle resonator. The visible light emission due to third harmonic generation (THG) was observed in both the output of a tapered fiber and the optical microscope images, which identify the axial mode profiles. SFG enabled by three- and four-wave mixing processes between the pump light and the light generated via SRS was also observed. Second Harmonic generation (SHG) and the SFG are enabled by χ² induced in silica by surface effects and multipole excitations.

Equivalent plane of reflection in graphene and single-layer Boron-Nitride

Michele Merano

Doc ID: 278835 Received 14 Oct 2016; Accepted 25 Nov 2016; Posted 28 Nov 2016  View: PDF

Abstract: Optical beam shifts from a free-standing two-dimensional atomic crystal are investigated. In contrast to a three-dimensional crystal the magnitude of the Goos-Hänchen shift depends on the surface susceptibility of the crystal and not on the wavelength of the incident light beam. The surface conductivity of the atomically thin crystal is less important in this context because it enters in the expression of the shifts only as a second order parameter. In analogy to a three-dimensional crystal the magnitudes of the Imbert-Fedorov shift and of the angular shifts depend respectively on the wavelength and on the square of the beam angular aperture.

Plasmonic structure: fiber grating formed by gold nanorods on a tapered fiber

Gautam Das, Joshua Trevisanutto, and Apichart Linhananta

Doc ID: 279088 Received 20 Oct 2016; Accepted 25 Nov 2016; Posted 28 Nov 2016  View: PDF

Abstract: The authors demonstrated the fabrication of a fiber Bragg grating (FBG)-like plasmonic nanostructure on the surface of a tapered optical fiber using gold nanorods (GNRs). A multimode optical fiber (MMF) with core and cladding diameters of 105 µm and 125 µm, respectively, was used to make a tapered fiber using a dynamic etching process. The tip dimeter was ~ 100 nm. Light from a laser was coupled to the untapered end of the fiber, which produced a strong evanescent field around the tapered section of the fiber. The gradient force due to the evanescent field trapped the gold nanorods on the surface of the tapered fiber. The authors explored the effect on the distribution of gold nanorods caused by the evanescent field produced by laser at different wavelengths. The plasmonic structure will be a good candidate for sensing based on surface enhanced Raman scattering.

High spatial resolution distributed optical fibre dynamic strain sensor with enhanced frequency and strain resolution

Ali Masoudi and T. Newson

Doc ID: 278834 Received 19 Oct 2016; Accepted 24 Nov 2016; Posted 28 Nov 2016  View: PDF

Abstract: A distributed optical fibre dynamic strain sensor with high spatial and frequency resolution is demonstrated. The sensor which uses φ-OTDR interrogation technique exhibited a higher sensitivity thanks to an improved optical arrangement and a new signal processing procedure. The proposedsensing system is capable of fully quantifying multiple dynamic perturbations along a 5km long sensing fibre with a frequency and spatial resolution of 5Hz and 50cm, respectively. The strain resolution of the sensor was measured to be 40nε.

Cascaded third-harmonic-generation with one KDP crystal

zhengping wang, hongwei qi, fapeng yu, Xun Sun, Xin-guang Xu, and Xian Zhao

Doc ID: 279106 Received 20 Oct 2016; Accepted 23 Nov 2016; Posted 29 Nov 2016  View: PDF

Abstract: For KH2PO4 (KDP) crystal, the phase-matching directions of type-II second-harmonic-generation (SHG) and type-II third-harmonic-generation (THG) for 1 μm lasers are almost identical, i.e. at (θ = 60⁰, Φ = 0⁰) around. Utilizing this special property, we designed a THG converter based on one KDP crystal. A quarter-wave (λ/4) plate was used to adjust the polarization of the SHG wave, and a round-trip optical path was used to realize the SHG and THG procedures, successively. When the fundamental light source was a 1064 nm, 40 ps pulse laser, the maximum THG output at 355 nm was 1.13 mJ, and the highest THG conversion efficiency was 30.7%. As we have known, it is the first time that the cascaded frequency up-conversion processes are realized in one bulk nonlinear optical (NLO) crystal. This method possesses many advantages for the future applications, including high efficiency, wide working waveband, low cost, and applicability to many other crystals like DKDP, ADP, DADP, GdxY1-xCOB, etc.

New approach for power scaling solid-state lasers with intracavity motion

W. Clarkson, Matthew Eckold, and Jacob Mackenzie

Doc ID: 278680 Received 14 Oct 2016; Accepted 23 Nov 2016; Posted 28 Nov 2016  View: PDF

Abstract: Solid-state lasers are typically limited by adverse thermal effects within the gain medium. In this paper we describe a new method for dramatically reducing thermal effects in an end-pumped solid-state laser by incorporating a rotating intracavity periscope in the resonator to spatially separate the lasing and thermal processes. In contrast to previous examples of moving solid-state lasers our approach keeps the gain medium stationary simplifying the heat removal arrangement. This scheme has been applied to a Nd:YAG laser yielding an output power of 120 W at 1.064 μm, limited by available pump power. Analysis suggests that scaling to much higher power is feasible with the appropriate laser design.

Spatially Localized, “See-through-wall” Temperature Measurements in a Flow Reactor using Radar REMPI

Mark GRAGSTON, YUE WU, zhili zhang, and Joseph Miller

Doc ID: 280153 Received 07 Nov 2016; Accepted 23 Nov 2016; Posted 29 Nov 2016  View: PDF

Abstract: “See-through-wall” coherent microwave scattering from Resonance Enhanced Multiphoton Ionization (REMPI) for rotational temperature measurements of molecular oxygen has been developed and demonstrated in a flow reactor at atmospheric pressure. Through limited, single-ended optical access, a laser beam was focused to generate local ionization of molecular oxygen in a heated quartz flow reactor enclosed by ceramic heating elements. Coherent microwaves were transmitted, and the subsequent scattering off the laser-induced plasma was received, through the optically opaque ceramic heater walls and used to acquire rotational spectra of molecular oxygen and determine temperature. Both axial and radial air-temperature profiles were obtained in the flow reactor with an accuracy of ±20 K (±5%). The experimental results show good agreement with a steady-state computational heat transfer model. This technique shows great potential for non-invasive, high-fidelity measurement of spatially localized temperature and radical species concentration in combustion kinetic experiments and confined combustors constructed of advanced ceramic materials in which limited or non-existing optical access hinders usage of conventional optical diagnostic techniques to quantify thermal non-uniformity

Mid-IR absorption spectroscopy of heavy water using a silicon-on-sapphire waveguide

Alvaro Casas-Bedoya, Neetesh Singh, Darren Hudson, Andrew Read, Eric Magi, and Benjamin Eggleton

Doc ID: 278325 Received 07 Oct 2016; Accepted 22 Nov 2016; Posted 22 Nov 2016  View: PDF

Abstract: We demonstrate a compact silicon-on-sapphire (SOS) strip waveguide sensor for mid-IR absorption spectroscopy. This device can be used for gas and liquid sensing, especially to detect chemically similar molecules and precisely characterise extremely absorptive liquids that are difficult to detect by conventional infrared transmission techniques. We reliably measure concentrations up to 0.25% of heavy water (D2O) in a D20 - H2O mixture at its maximum absorption band at around 4 µm. This CMOS compatible SOS D2O sensor is promising for applications such as measuring body fat content or detection of coolant leakage in the nuclear reactors.

Frequency-modulated microwave generation with feedback stabilization using an optically injected semiconductor laser

Jun-Ping Zhuang, Xiao-Zhou Li, Song-Sui Li, and Sze-Chun Chan

Doc ID: 279845 Received 01 Nov 2016; Accepted 21 Nov 2016; Posted 21 Nov 2016  View: PDF

Abstract: Generation of frequency-modulated continuous-wave (FMCW) microwave signals is investigated using the period-one (P1) dynamics of a semiconductor laser. A modulated optical injection drives the laser into P1 oscillation with a modulated microwave frequency, while adding a feedback to the injection reduces the microwave phase noise. Using simply a single-mode laser, the tunability of P1 dynamics allows for a wide tuning of the central frequency of the FMCW signal. A sweep range reaching 7.7 GHz is demonstrated with a sweep rate of 0.42 GHz/ns. When the external modulation frequency matches the reciprocal of the feedback delay time, feedback stabilization is manifested as an increase of the frequency comb contrast by 30 dB for the FMCW microwave signal.

Complex degree of coherence measurement for classical statistical fields

Sergey Ponomarenko, Xianlong Liu, Yangjian Cai, Yahong Chen, Lin Liu, and Fei Wang

Doc ID: 279005 Received 21 Oct 2016; Accepted 21 Nov 2016; Posted 29 Nov 2016  View: PDF

Abstract: We propose a new method for measuring real and imaginary parts of the complex degree of coherence of a classical field obeying Gaussian statistics. Our method is based on mixing incoherently a coherent Gaussian beam, a local oscillator, and the statistical field. We stress that our approach is especially beneficial for revealing the complex degree of coherence of inhomogeneous two- dimensional fields. As an illustration, we report the complex degree of coherence measurement of a complex Gaussian correlated beam. Our method can find applications to image transmission and recovery.

Tripartite non-separability in classical optics

Antonio Khoury, W Balthazar, Carlos Eduardo Souza, Dilson Caetano, Ernesto Galvao, and Jose Augusto Huguenin

Doc ID: 278234 Received 07 Oct 2016; Accepted 21 Nov 2016; Posted 21 Nov 2016  View: PDF

Abstract: It is possible to prepare classical optical beams which cannot be characterized by a tensor product of vectors describing each of their degrees of freedom. Here we report the experimental creation of such a non-separable, tripartite GHZ-like state of path, polarization and transverse modes of a classical laser beam. We use a Mach-Zehnder interferometer with an additional mirror and other optical elements to perform measurements that violate Mermin's inequality. This demonstration of a classical optical analogue of tripartite entanglement paves the path to novel optical applications inspired by multipartite quantum information protocols.

Active Gratings Tuned by Thermoplasmonics-induced Phase Transition in Vanadium Dioxide Thin Films

Binhe Wu, Xiaofeng Xu, and Chunrui Wang

Doc ID: 278780 Received 19 Oct 2016; Accepted 20 Nov 2016; Posted 21 Nov 2016  View: PDF

Abstract: We propose and investigate an active grating of gold metallic structure on vanadium dioxide (VO$_2$) thin film illuminated by an intense light. Nonuniform phase transition in VO$_2$ film is expected due to the thermoplasmonics effect where the plasmonic-induced light absorption features an enhanced local heat generation at nanometer-scale. The spatial profiles of the electric field, the heat generation, the temperature distribution as well as the temperature-dependent dielectric parameters in VO$_2$ film are solved numerically in a self-consistent manner. Our results show that the evolution of the metallic and semiconducting phases of VO$_2$ changes the effective dielectric environment of the grating and modifies its optical response in a controlled way. The interplay of the thermoplasmonics effect and the phase transition processes can thus provide another degree of freedom in designing optical modulators or switches which are remotely tunable via incident light.

Terahertz thermometry of gold nanospheres in water

Jeffrey Davis, Fabio Novelli, and James Chon

Doc ID: 276457 Received 23 Sep 2016; Accepted 20 Nov 2016; Posted 21 Nov 2016  View: PDF

Abstract: The photo-thermal effects of plasmonic nanoparticles are promising for cancer therapies. These treatments would greatly benefit from real time, multi-scale temperature mapping by non-invasive means. Here we show that intense terahertz time domain spectroscopy can be used as a non-contact and high resolution thermometer of water solutions. Using this technique we measure the temperature change, triggered by femtosecond amplified laser pulses, of a solution of water and gold nanospheres. Extensions of this ultra-fast and non-invasive technique could open the door to real-time micro-thermometry of single cells without fluorescent labels.

Acoustic-actuated optical coherece angiography


Doc ID: 277590 Received 27 Sep 2016; Accepted 20 Nov 2016; Posted 21 Nov 2016  View: PDF

Abstract: Optical coherence tomography (OCT) angiography requires high sensitivity and image penetration for detailed microvascular monitoring. Unfortunately, no effective contrast-medium-enhanced scheme is currently available for imaging improvement. We here propose the simultaneous use of gas-filled microbubbles (MBs) and acoustic actuation to enhance the imaging contrast of OCT angiography. OCT-synchronized acoustic actuation was applied in the presence of MBs, and different moving object tracking angiographic algorithms were tested in in-vitro tubing and in-vivo mouse experiments. This scheme significantly enhanced the OCT angiography performance, including its sensitivity and penetration, and should advance the utilization of OCT as an effective microvascular diagnostic tool.

Output features of optical parametric chirped pulse amplification in LiB3O5 near 800 nm at different phase matching geometries

Xiaoyan Liang, Liu Xiaodi, and Lu Xu

Doc ID: 279770 Received 02 Nov 2016; Accepted 20 Nov 2016; Posted 22 Nov 2016  View: PDF

Abstract: We theoretically and experimentally investigated the output beam quality and wavefront distortion in four different phase-matching geometries in LBO-OPCPA at 800nm: broadband noncollinear geometry, collinear geometry, pump-idler Poynting vector collinear (Sp//Si) geometry, and pump-signal Poynting vector collinear (Sp//Ss) geometry. It was found that the output profile is closely related to the noncollinear angle between Poynting vectors of parametric waves. However, the wavefront evolution depends mainly on angles between wave vectors. Broadband noncollinear geometry has the largest spatial modulation and wavefront distortion. Good output beam quality can be achieved in collinear geometry with little wavefront distortion, but the bandwidth is only approximately 10 nm. The Sp//Ss and Sp//Si configurations result in a bandwidth of more than 20 nm with enhanced beam quality and small wavefront distortion. The two geometries have different output features wherein the former has a relatively lower modulation and the latter shows smaller wavefront distortion.

Hybrid wavelength- and frequency-division multiplexed fiber laser sensor array

shengchun liu, Xue Dong, Xiujuan Yu, xuefeng chen, and Chao Tian

Doc ID: 278600 Received 18 Oct 2016; Accepted 20 Nov 2016; Posted 05 Dec 2016  View: PDF

Abstract: The paper describes a hybrid multiplexing scheme for multi-longitudinal mode fiber laser sensor array by combining wavelength-division multiplexing and frequency-division multiplexing technique. The proposed multiplexing system consists of many subgroups, each of which has many fiber laser sensors with approximately equal laser operating wavelength, but different cavity length. Each sensor in one subgroup can be interrogated by using frequency-division multiplexing technology because of different sensors with different beat frequency. For different subgroup, they are characteristic of different laser operating wavelength. Each subgroup can be divided to the designed channel by dense wavelength-division multiplexers. At last, a 4×4 sensor multiplexing system was experimentally validated. The strain or temperature applied on each sensor was successfully extracted. Theoretically, the multiplexing system can address up to 725 fiber laser sensors. By combining FDM and WDM, the hybrid multiplexing system provides a dramatic increase for the multiplexing number. It greatly reduces the weight, volume, and cost of each sensor, and offers a competitive scheme for large-scale monitoring system.

Enhanced Visualization of Peripheral Retinal Vasculature with Wavefront Sensorless Adaptive Optics OCT Angiography in Diabetic Patients

James Polans, David Cunefare, Brenton Keller, Elijah Cole, Priyatham Mettu, Scott Cousins, Michael Allingham, Joseph Izatt, and Sina Farsiu

Doc ID: 279173 Received 24 Oct 2016; Accepted 19 Nov 2016; Posted 21 Nov 2016  View: PDF

Abstract: Optical coherence tomography angiography (OCTA) is a promising technique for the non-invasive visualization of vessel networks in the human eye. We debut a system capable of acquiring wide field-of-view (>70°) OCT angiograms without mosaicking. Additionally, because the aberrations of the human eye vary across a large field-of-view, we report on enhancing the visualization of peripheral microvasculature using wavefront sensorless adaptive optics (WSAO). We employed a fast WSAO algorithm that enabled wavefront correction in <2 seconds by iterating the mirror shape at the speed of OCT B-scans rather than volumes. Also, we contrasted ~5° field-of-view OCTA angiograms acquired in the periphery with and without WSAO correction. Preliminary observations demonstrated that the location of 5° images could be identified directly from the wide field-of-view angiogram. A pilot study on a normal subject and patients with diabetic retinopathy showed the impact of utilizing WSAO for OCTA when visualizing peripheral vasculature pathologies.

Mode analysis of higher-order transverse-mode correlation beams in turbulent atmosphere

Hakob Avetisyan and Carlos Monken

Doc ID: 280776 Received 18 Nov 2016; Accepted 18 Nov 2016; Posted 29 Nov 2016  View: PDF

Abstract: Due to the transfer of the angular spectrum of the pump beam to the two-photon state in spontaneous parametric down-conversion the generated twin photons are entangled in their spatial degrees of freedom. This spatial entanglement can be observed through correlation measurements in any set of modes one may choose to perform measurements. Choosing, e.g., Hermite-Gaussian (HG) set of spatial modes as a basis one can observe correlations present in their spatial degrees of freedom. In addition, these set of modes can be used as alphabets for quantum communication. For global quantum communication purposes, we derive an analytic expression for two-photon detection probability in terms of HG modes taking into account the effects of the turbulent atmosphere. Our result is more general as it accounts for the propagation of both, signal and idler photons through the atmosphere, as opposed to other works considering one of the photons’ propagation in vacuum. We show that while the restrictions on both the parity and order of the down-converted HG fields no longer hold due to the crosstalk between modes when propagating in the atmosphere, the crosstalk is not uniform: there are more robust modes that tend to keep the photons in them. These modes can be employed in order to increase the fidelity of quantum communication.

Simultanous two-wavelength phase unwrapping using external module for multiplexing off-axis holography

Natan Shaked and Nir Turko

Doc ID: 278002 Received 03 Oct 2016; Accepted 17 Nov 2016; Posted 01 Dec 2016  View: PDF

Abstract: We present a dual-wavelength external holographic microscopy module for quantitative phase imaging of 3D structures with extended thickness range. This is done by simultaneous acquisition of two off-axis interferograms, each of which at a different wavelength, and generation of a synthetic wavelength, which is larger than the sample optical thickness, allowing two-wavelength unwrapping. The simultaneous acquisition is carried out by using optical multiplexing of the two interferograms onto the camera, where each of them has orthogonal off-axis interference fringe direction in relation to the other one. We used the system to quantitatively image a 7.96 µm step target and 30.5 µm circular copper pillars.

Compressive fluorescence imaging using a multi-core fiber and spatially-dependent scattering

Mark Foster, Jaewook Shin, and Bryan Bosworth

Doc ID: 279001 Received 19 Oct 2016; Accepted 17 Nov 2016; Posted 05 Dec 2016  View: PDF

Abstract: We demonstrate two-dimensional imaging using a multi-core fiber with a scattering distal tip and compressed sensing signal acquisition. We illuminate objects with randomly structured yet deterministic speckle patterns generated by a coherent light source separately coupled through each fiber core to a ground glass diffuser at the distal end. Using the characterized speckle patterns and the total light collected from the object, we computationally recover pixelation-free object images with 10 times more pixels than the number of cores. The proposed imaging system is insensitive to bending of the fiber and extremely compact, making it suitable for minimally-invasive endomicroscopy.

193 fs from an Yb:YAG Oscillator Mode-Locked Using Nonlinear Polarization Rotation via Type I SHG with Intrinsic Dispersion Compensation

Christian Fries, Christoph Schäfer, Christian Theobald, and Johannes Lhuillier

Doc ID: 278515 Received 13 Oct 2016; Accepted 17 Nov 2016; Posted 18 Nov 2016  View: PDF

Abstract: The mode-locking technique utilizing nonlinear polarization rotation via Type I second harmonic generation is demonstrated experimentally on the femtosecond timescale. The usually narrow spectral bandwidth of the loss modulation was broadened via a double crystal approach, which allows for mode-locking broad band gain media. We experimentally prove the predicted advantages of the technique to be correct utilizing intrinsic dispersion compensation and GVM management to produce 193 fs pulses. This eliminates the need for dispersion compensating elements. The technique can be applied to high power lasers at any wavelength where a suitable SHG process is possible.

{Dispersion measurements in Ocular Media using a dual wavelength swept source Optical Coherence Tomography system

Bastian Braeuer, Stuart Murdoch, and Frederique Vanholsbeeck

Doc ID: 278646 Received 12 Oct 2016; Accepted 17 Nov 2016; Posted 18 Nov 2016  View: PDF

Abstract: Optical coherence tomography (OCT) has proved to be a powerful tool for the detection of microstructure in tissue. Label free tissue differentiation on a micron scale is a promising and powerful technique for segmentation. This paper describes a technique using a dual wavelength OCT system to image the eye. We measure the walk-off between interfaces in A-scans, taken at two different wavelengths, to calculate the average group velocity dispersion parameter of each segment of the eye. We present measurements of the dispersion of the cornea and the aqueous humour in rat eyes.

Spectroscopy and continuous wave laser performance of Yb3+:LuAlO3 crystal

Alexander Rudenkov, Viktor Kisel, Anatol Yasukevich, KARINE HOVHANNESYAN, Ashot Petrosyan, and Nikolai Kuleshov

Doc ID: 278685 Received 13 Oct 2016; Accepted 16 Nov 2016; Posted 18 Nov 2016  View: PDF

Abstract: Crystal growth, polarized spectroscopic properties, lifetime measurements and CW laser performance under diode pumping of a new Yb3+-doped LuAlO3 crystal (Yb:LuAP) are reported for the first time to the best of our knowledge. The maximum absorption cross section of 6.6•10-20cm2 at 978.5nm was determined for E//c polarization. The radiative lifetime of 2F5/2 manifold of Yb3+ ions in LuAP was measured to be 475µs. CW laser action was demonstrated with output powers up to 9.6W and slope efficiencies up to 84.5%. 82nm-tunability range was demonstrated for E//c polarization.

Phase-sensitive OTDR probe pulse shapes robust against modulation-instability fading

María R. Fernández-Ruiz, Hugo Martins, Juan Pastor Graells, Sonia Martin-Lopez, and Miguel Gonzalez Herraez

Doc ID: 278791 Received 18 Oct 2016; Accepted 16 Nov 2016; Posted 18 Nov 2016  View: PDF

Abstract: Typical phase-sensitive OTDR (φOTDR) schemes rely on the use of coherent rectangular-shaped probe pulses. In these systems, there is a trade-off between the signal-to-noise ratio (SNR), spatial resolution and operating range of the φOTDR system. To increase any of these parameters, an increase in the pulse peak power is usually indispensable. However, as it is well-known, there is a limit in the allowable increase in probe power due to the onset of undesired nonlinear effects such as modulation instability. In this Letter, we perform an analysis of the effect of the probe pulse shape on the visibility fading due to modulation instability. In particular, four different temporal profiles are chosen, namely, rectangular, Gaussian, triangular and super-Gaussian (order 2). Our numerical and experimental analyses reveal that the use of triangular or Gaussian-like pulses can significantly inhibit the visibility fading issues. As such, an increase in the range up to two-fold for the same pulse energy (i.e., SNR) and spatial resolution can be achieved, as compared with the results obtained when using rectangular pulses. This is due to a more robust behavior of the Gaussian and triangular pulses against the Fermi-Pasta-Ulam (FPU) recurrence occurring in modulation instability.

Iterative creation and sensing of quantum states of light

Brannon Klopfer, Thomas Juffmann, and Mark Kasevich

Doc ID: 278372 Received 11 Oct 2016; Accepted 16 Nov 2016; Posted 16 Nov 2016  View: PDF

Abstract: The iterative interaction of a photon with a sample can lead to increased sensitivity in measuring the properties of the samples, such as its refractive index or birefringence. Here we show that this principle can also be used to generate and sense quantum states of light. In particular we demonstrate a technique to generate states with high orbital angular momentum using a single vortex phase plate. This is accomplished by placing the phase plate in a self-imaging cavity such that light interacts with it multiple times; for an ideal phase plate, this is equivalent to iterative applications of the angular momentum operator. Using a discrete vortex phase plate, we show that our setup realizes a high dimensional generalization of the Pauli matrix σ_x, and that the created states show sub-diffraction limited features that might find applications in structured illumination microscopy.

Nodeless Hollow-Core Fiber for Visible Spectral Range

Yingying Wang, Shoufei Gao, Pu Wang, Xiaolu Liu, shuai gu, and Hong Chang

Doc ID: 276495 Received 28 Sep 2016; Accepted 16 Nov 2016; Posted 30 Nov 2016  View: PDF

Abstract: We report on the first hollow-core fiber (HCF) whose fundamental transmission band covers almost the whole visible spectral window starting from 440 nm. This HCF, in the form of nodeless structure (NL-HCF), exhibits unprecedented optical performance in terms of low transmission attenuation of 80 dB/km @ 532 nm, broad transmission bandwidth from 440 nm to 1500 nm, low bending loss of 0.2 dB/m @ 532 nm under 8 cm bending radius and single mode profile. When launched to high power picosecond laser systems at 532 nm, the fiber, exposed to ambient air, could easely deliver a 80 ps, 58 MHz, 32 W average power laser pulse with no damage and a 20 ps, 1 kHz high energy laser pulse with a damage threshold in excess of 144 uJ at fiber output. A proof-of-concept experiment on Raman spectroscopy in ambient air shows the significance of this broadband visible guiding HCF for interdisciplinary applications in nonlinear optics, ultrafast optics, lasers,spectroscopy, biophotonics, material processing, etc.

Equalized estimation of Stokes parameters in the presence of Poisson noise for any number of polarization analysis states

Francois Goudail

Doc ID: 279442 Received 24 Oct 2016; Accepted 15 Nov 2016; Posted 21 Nov 2016  View: PDF

Abstract: Estimation of the Stokes vector is based on projecting the input light on a number N of polarization analysis states. We address the optimization of the distribution of these analysis states on the Poincaré sphere in the presence of signal-dependent Poisson shot noise for an arbitrary value of N. We show that if this distribution forms a spherical 3 design, the Stokes vector is estimated with minimal equally weighted variance (EWV) and with estimation variances of the last three Stokes parameter equal and independent of the input Stokes vector. We also demonstrate that in the presence of Poisson shot noise, the estimation signal to noise ratio is independent of N, whereas in the presence of signal independent additive noise, it is proportional to 1/N, which means that there is a precision loss in increasing the number of measurements.

Spatially-Resolved Individual Particle Spectroscopy using Photothermal Modulation of Mie Scattering

Ryan Sullenberger, Shawn Redmond, David Crompton, Alexander Stolyarov, and William Herzog

Doc ID: 279697 Received 01 Nov 2016; Accepted 14 Nov 2016; Posted 21 Nov 2016  View: PDF

Abstract: We report a photothermal modulation of Mie scattering (PMMS) method that enables concurrent spatial and spectral discrimination of individual micron-sized particles. This approach provides a direct measurement of the ‘fingerprint’ infrared absorption spectrum with the spatial resolution of visible light. Trace quantities (tens of picograms) of material were deposited onto an infrared-transparent substrate and simultaneously illuminated by a wavelength-tunable intensity-modulated quantum cascade pump laser and a continuous-wave 532 nm probe laser. Absorption of the pump laser by the particles results in direct modulation of the scatter field of the probe laser. The probe light scattered from the interrogated region is imaged onto a visible camera, enabling simultaneous probing of spatially-separated individual particles. By tuning the wavelength of the pump laser, the IR absorption spectrum is obtained. Using this approach, we measured the infrared absorption spectra of individual 3 μm PMMA and silica spheres. Experimental PMMS signal amplitudes agree with modeling using an extended version of Mie scattering theory for particles on substrates, enabling the prediction of the PMMS signal magnitude based on the material and substrate properties.

Coherently combined master oscillator fiber power amplifiers for Advanced Virgo

Li-Wei Wei, Catherine Man, and Frédéric Cleva

Doc ID: 278274 Received 18 Oct 2016; Accepted 14 Nov 2016; Posted 17 Nov 2016  View: PDF

Abstract: Stable low-noise high-power lasers are indispensable in advancing the strain sensitivity of interferometric gravitational wave detectors. Advanced LIGO and Advanced Virgo are currently under commissioning and require about 200 W of single-frequency laser power, while future detector design may require up to the order of 500 W. In this paper we present the design and a first experimental demonstration of the laser system for Advanced Virgo which is based on coherently combined fiber laser amplifiers. We show the long-term performance of two 40 W fiber laser amplifiers as well as their characterization in terms of beam quality, power noise, phase noise and beam pointing. Moreover, a simple and compact setup utilizing fibered modulators and actuators for the coherent beam combination of these two fiber laser amplifiers is reported. A combination efficiency of about 96 % was achieved and no spurious noise was observed.

GHz bandwidth semipolar (11-22) InGaN/GaN light-emitting diodes

Duc Dinh, Zhiheng Quan, Brendan Roycroft, Peter Parbrook, and Brian Corbett

Doc ID: 279322 Received 25 Oct 2016; Accepted 14 Nov 2016; Posted 17 Nov 2016  View: PDF

Abstract: We report on the electrical-to-optical modulation bandwidths of non-mesa-etched semipolar (11-22) InGaN/GaN light-emitting diodes (LEDs) operating at 430-450nm grown on high quality (11-22) GaN templates, which were prepared on patterned r-plane (10-12) sapphire substrates. The measured frequency response at -3dB of the LEDs was up to 1GHz. A high back-to-back data transmission rate of above 2.4Gbps is demonstrated using a non-return-to-zero on-off keying modulation scheme. This indicates that (11-22) LEDs are suitable Gbps data transmission for use in visible-light communication applications.

Spatiotemporal Characterization of Supercontinuum Extending from the Visible to the Mid-Infrared in Multimode Graded-Index Optical Fiber

Alessandro Tonello, Katarzyna Krupa, Christophe Louot, Vincent COUDERC, Marc FABERT, Romain Guenard, Badr SHALABY, Dominique Pagnoux, Philippe Leproux, Abdelkrim Bendahmane, Richard Dupiol, Guy Millot, and Stefan Wabnitz

Doc ID: 279740 Received 04 Nov 2016; Accepted 13 Nov 2016; Posted 21 Nov 2016  View: PDF

Abstract: We experimentally demonstrate that pumping a graded-index multimode fiber with sub-ns pulses from a microchip Nd:YAG laser leads to spectrally flat supercontinuum generation with a uniform bell-shaped spatial beam profile extending from the visible to the mid-infrared at 2500 nm. We study the development of the supercontinuum along the multimode fiber by the cut-back method, which permits us to analyze the competition between the Kerr-induced geometric parametric instability and stimulated Raman scattering. We also performed a spectrally resolved temporal analysis of the supercontinuum emission.

Reply on the comment of Novotny et al regarding our paper [Opt. Lett. 40(15), 3536 (2015)]

Nikolay Chtchelkatchev, Evgeny Andrianov, and A. Pukhov

Doc ID: 275255 Received 07 Sep 2016; Accepted 09 Nov 2016; Posted 09 Nov 2016  View: PDF

Abstract: We reply on comment regarding our paper [Opt. Lett. 40(15), 3536 (2015)] where dissipative driven bosonic mode strongly coupled to a two-level system is studied. We show that authors of the comment erroneously claim that Monte Carlo sampling is insufficient. More important is the basic statement of the comment about vanishing width of the spectral line: then plasmon spectral line at large external field vanishes! This strange statement contradicts common knowledge. Authors of the comment do not distinguish averages of observables from quasiaverages that are quite different in multistable systems where \textbf{erhgodisity} is challenged.

Temporal jitter in free-running InGaAs/InP single-photon avalanche detectors

Gianluca Boso, Hugo Zbinden, Boris Korzh, and Emna Amri

Doc ID: 278289 Received 07 Oct 2016; Accepted 07 Nov 2016; Posted 07 Nov 2016  View: PDF

Abstract: Negative-feedback avalanche diodes (NFADs) provide a practical solution for different single-photon counting applications requiring free-running mode operation with low after-pulsing probability. Unfortunately, the time jitter has never been as good as for gated InGaAs/InP single-photon avalanche diodes (SPADs).Here we report on the time jitter characterization of InGaAs/InP based NFADs with a particular focus on the temperature dependence and the effect of carrier transport between the absorption and the multiplication regions. Values as low as 52 ps were obtained at an excess bias voltage of 3.5 V.

Multimode photon-exciton coupling in an organic-dye-attached photonic quasicrystal

Ruwen Peng, Kun Zhang, Yue Xu, Tianyong Chen, Hao Jing, Wenbo Shi, Bo Xiong, and Mu Wang

Doc ID: 278421 Received 10 Oct 2016; Accepted 05 Nov 2016; Posted 15 Nov 2016  View: PDF

Abstract: In this letter, we presents hybrid strong coupling between multiple photonic modes and the excitons in an organic-dye-attached photonic quasicrystal. The excitons effectively interact with the photonic modes offered by the photonic quasicrystal, and multiple hybrid polariton bands are demonstrated in both experiments and calculations. Furthermore, by retrieving measured dispersion maps, we get the mixing fractions of the photonic modes and excitons, and show that the polariton bands inherit not only the energy dispersion features but also the damping behaviors from both the photonic modes and excitons. Our investigation may inspire related studies on multimode light-matter interactions and achieve some potential applications on multimode sensors.

Achievable information rates estimates in optically-amplified transmission systems using nonlinearity compensation and probabilistic shaping

Tianhua Xu, Daniel Semrau, Nikita Shevchenko, Milen Paskov, Alex Alvarado, Robert Killey, and Polina Bayvel

Doc ID: 276023 Received 19 Sep 2016; Accepted 05 Nov 2016; Posted 07 Nov 2016  View: PDF

Abstract: Achievable information rates (AIRs) of wideband optical communication systems using ~40 nm (~5 THz) EDFA and ~100 nm (~12.5 THz) distributed Raman amplification are estimated based on a first-order perturbation analysis. The AIRs of each individual channel have been evaluated for DP-64QAM, DP-256QAM, and DP-1024QAM modulation formats. The impact of full-field nonlinear compensation (FF-NLC) and probabilistically shaped constellations using a Maxwell-Boltzmann distribution were studied and compared to electronic dispersion compensation. It is found that a probabilistically shaped DP-1024QAM constellation combined with FF-NLC yields AIRs of ~75 Tbit/s for the EDFA scheme and ~2 Tbit/s for the Raman amplification scheme over 2000 km standard single mode fibre transmission.

Generation of adjustable multi-octave supercontinuum under near-IR filamentation in gaseous, supercritical and liquid carbon dioxide

Evgeniy Mareev, Victor Bagratashvili, Nukita Minaeev, Fedor Potemkin, and Viacheslav Gordienko

Doc ID: 278007 Received 03 Oct 2016; Accepted 03 Nov 2016; Posted 04 Nov 2016  View: PDF

Abstract: We demonstrate a new source of efficient supercontinuum generation (SC) from high-pressure gas, liquid and supercritical fluid CO2 aggregate states, under near-IR femtosecond filamentation. The high nonlinear properties (comparable with condensed matter) leads to significant overcoming on critical power of self-focusing even at microjoule laser pulse energies and the femtosecond filamentation is occurred. The generated at such regime SC spans more than two octaves (from 400nm up to 2μm). The most efficient SC generation is achieved in liquid CO2 (p=65 bar, T= ͦC). In contradistinction to the atomic gas (Xe) the molecular vibrations significantly modifies the SC spectrum. It leads to the generation of a bright peak in a 1.4-1.9μm wavelength region, which position could be finely tuned by the pressure and temperature control.

Using a redox-sensitive phosphorescent probe for optical evaluation of intracellular redox environment

Qiang Zhao, Shujuan Liu, Yana Zhu, Huanjie Wei, Zejing Chen, Song Guo, and Na Zhou

Doc ID: 273374 Received 08 Aug 2016; Accepted 03 Nov 2016; Posted 28 Nov 2016  View: PDF

Abstract: A reducing intracellular environment is necessary for living cells. Here a redox-sensitive phosphorescent probe Ir-NO has been developed for evaluating the redox environment in living cells. Upon addition of reducing molecules, such as glutathione (GSH) and ascorbic acid (AsA), the phosphorescent intensity of probe is turned on, and the emission lifetime is elongated evidently. Furthermore, this probe has been used for optical imaging of the intracellular reducing environment by utilizing confocal laser scanning microscopy (CLSM) and phosphorescence lifetime imaging microscopy (PLIM).

Thermal poling of silica optical fibers using novel liquid electrodes

Pier Sazio, Francesco De Lucia, Derek Keefer, and Costantino Corbari

Doc ID: 276032 Received 16 Sep 2016; Accepted 25 Oct 2016; Posted 27 Oct 2016  View: PDF

Abstract: Thermal poling is a well-known technique for inducing second-order nonlinearities in centrosymmetric silica optical fibers. However, some 25 years since its discovery, there still remain a number of issues that prevent the realization of very long length, highly efficient all-fiber nonlinear device applications that includes frequency conversion or sources of polarization-entangled photon pairs. In this paper we report a thermal poling method that utilizes a novel range of liquid metal and aqueous electrodes embedded into the optical fibers. We demonstrate that it is possible to pole samples that are potentially meters in length, characterized by very low losses for efficient SHG processes. The estimated effective value of Chi(2) (0.1 pm/V) obtained using Mercury electrodes is the highest reported in periodically poled silica fibers.

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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