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Accepted papers to appear in an upcoming issue

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4.2 PW, 20 fs Ti:Sapphire Laser at 0.1 Hz

Jae Hee Sung, H. W. Lee, J. Y. Yoo, JW Yoon, Chang Won Lee, Jeong Moon Yang, YeonJoo Son, Yong Ha Jang, Seong Ku Lee, and Chang Hee Nam

Doc ID: 291023 Received 22 Mar 2017; Accepted 20 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We demonstrated the generation of 4.2-PW laser pulses at 0.1 Hz from a chirped-pulse amplification Ti:sapphire laser. The cross-polarized wave generation and the optical parametric chirped-pulse amplification stages were installed in the frontend for the prevention of the gain narrowing and for the compensation of the spectral narrowing in the amplifiers, obtaining the spectral width of amplified laser pulses of 84 nm (FWHM) and, additionally, enhancing the temporal contrast. The amplified laser pulses of 112 J after the final booster amplifier were compressed to the pulses with 83 J at 19.4 fs with a shot-to-shot energy stability of 1.5% (RMS). This 4 PW laser will be a workhorse for exploring high field science.

Multiple wavelength stabilization on a single optical cavity using sideband locking technique

Gianmaria Milani, Benjamin Rauf, Piero Barbieri, Filippo Bregolin, Marco Pizzocaro, Pierre Thoumany, Filippo Levi, and Davide Calonico

Doc ID: 287025 Received 28 Feb 2017; Accepted 19 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We implemented a compact, robust and stable device for simultaneous stabilization of lasers with different wavelengths used for the cooling and trapping of atoms in an Yb optical lattice clock. The lasers at 399 nm, 556 nm and 759 nm are locked to a single ultra-stable cavity using the sideband-locking technique, a modified version of the Pound-Drever-Hall method. For the most demanding stabilization here, the 556 nm laser, this system exhibits a 300 Hz linewidth. We observed a long term drift of less than 20 kHz per day at 759 nm that is suitable for operating the lattice laser with a light shift uncertainty below 1×10^{-18}. We successfully tested the system for operating the clock during a typical working day by simultaneously locking the three lasers to the cavity.

A high precise micro-displacement optical-fiber sensor based on surface plasmon resonance

Zongda Zhu, lu liu, Zhihai Liu, Yu Zhang, and Yaxun Zhang

Doc ID: 290272 Received 07 Mar 2017; Accepted 19 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We propose and demonstrate a novel optical-fiber micro-displacement sensor based on surface plasmon resonance (SPR) by fabricating a Kretchmann-configuration on graded-index multimode fiber (GIMMF). We employ a single mode fiber (SMF) to change the radial position of the incident beam as the displacement. In the GIMMF, the angle between light beam and fiber axis, which is closely related to resonance angle, is changed by the displacement, thus the resonance wavelength of fiber SPR shifts. This micro-displacement fiber sensor has a wide detection range of 0-25μm, a high sensitivity of 10.32nm/μm and a nanometer resolution of 2nm, which transcends almost all of other optical fiber micro-displacement sensors. In addition, we also research that increasing the fiber grinding angle or medium refractive index can improve the sensitivity. This micro-displacement sensor will have a great significance in many industrial applications and provide a neoteric, rapid and accuracy optical measurement method in micro-displacement.

Third-harmonic blue light generation from Kerr clustered combs and dispersive waves

Shun Fujii, Takasumi Tanabe, Ryo Suzuki, and Takumi Kato

Doc ID: 290280 Received 07 Mar 2017; Accepted 19 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We demonstrated the generation of blue light emission (438 nm) via the third-harmonic process from an infrared pump by carefully engineering the dispersion of a high quality factor whispering gallery mode microcavity. We present two different approaches to obtaining broad bandwidth light. One is based on a clustered comb and the other employs a dispersive wave, and a broad Kerr comb spanning a half-octave is obtained. This allowed frequency conversion over a broad bandwidth ranging from 438 to 612 nm. This approach will enable the development of micro-scale light sources and frequency converters for future optical processing.

Non-reciprocal geometric phase in nonlinear frequency conversion

Kai Wang, Yu Shi, Alexander Solntsev, Shanhui Fan, Andrey Sukhorukov, and Dragomir Neshev

Doc ID: 285119 Received 13 Feb 2017; Accepted 18 Apr 2017; Posted 18 Apr 2017  View: PDF

Abstract: We describe analytically and numerically the geometric phase arising from nonlinear frequency conversion and show that such a phase can be made non-reciprocal by momentum-dependent photonic transition. Such non-reciprocity is immune to the shortcomings imposed by dynamic reciprocity in Kerr and Kerr-like devices. We propose a simple and practical implementation, requiring only a single waveguide and one pump, while the geometric phase is controllable by the pump and promises robustness against fabrication errors.

The Umov effect in single-scattering dust particles: Effect of irregular shape

Evgenij Zubko, ALYCIA WEINBERGER, Nataliya Zubko, Yuriy Shkuratov, and Gorden Videen

Doc ID: 291058 Received 20 Mar 2017; Accepted 18 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: The Umov effect manifests itself as an inverse correlation between the light-scattering maximum of positive polarization P_max and the geometric albedo A of target. In logarithmic scales, P_max is linearly dependent on A. This effect is long known in optics of particulate surfaces and, recently, it was extended for the case of single-scattering dust particles whose size is comparable to the wavelength of the incident light. In this work we investigate the effect of irregular shape on the Umov effect in single-scattering particles. Using the discrete dipole approximation (DDA), we model light scattering by two different types of irregularly shaped particles. Despite significant differences in their morphology, both types of particles reveal remarkably similar diagrams of log(P_max) vs. log(A). Moreover, in a power-law size distribution r^(–n) with n = 2.5 – 3.0 the Umov diagrams in both types of particles nearly coincide. This suggests little dependence on the shape of target particles in the retrieval of their reflectance using the Umov effect.

A scalable Fourier transform system for instantly structured illumination in lithography

Yan Ye, Fengchuan Xu, Guojun Wei, Yishen Xu, Donglin Pu, Linsen Chen, and Zhiwei Huang

Doc ID: 291410 Received 27 Mar 2017; Accepted 17 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We report the development of a unique scalable Fourier transform 4-f system for instantly structured illumination in lithography. In the 4-f system coupled with a 1-D grating and a phase retarder, the ±1st order of diffracted light from the grating serve as coherent incident sources for creating interference patterns on the image plane. By adjusting the grating and the phase retarder, the interference fringes with consecutive frequencies as well as their orientations and phase shifts can be generated instantly within a constant interference area. We demonstrate that by adapting this scalable Fourier transform system into lithography, the pixelated nano-fringe arrays with arbitrary frequencies and orientations can be dynamically produced in the photoresist with high variation resolution, suggesting its promising application for large area functional materials based on space-variant nanostructures in lithography.

Spatial Integration by a Dielectric Slab Waveguide andits Planar Graphene-based Counterpart

Farzad Zangeneh-Nejad and Amin Khavasi

Doc ID: 290328 Received 08 Mar 2017; Accepted 17 Apr 2017; Posted 18 Apr 2017  View: PDF

Abstract: Motivated by the recent progress in analog computing [Science 343, 160 (2014)], a new approach to perform spatial integration is presented using a dielectric slab waveguide. Our approach is indeed based on the fact that the transmission coefficient of a simple dielectric slab waveguide at its mode excitation angle matches the Green’s function of first order integration. Inspired by the mentioned dielectric-based integrator, we further demonstrate its graphene-based counterpart. The latter is not only reconfigurable but also highly miniaturized in contrast to the previously reported designs [Opt. Commun. 338, 457 (2015)]. Such integrators have the potential to be used in ultrafast analog computation and signal processing.

A multi-petawatt laser facility fully based on optical parametric chirped pulse amplification

Xiaoming Zeng, Kainan Zhou, Yanlei Zuo, Qihua Zhu, Jingqin Su, xiao wang, Xiaodong Wang, Xiaojun Huang, Xuejun Jiang, dongbin Jiang, Yi Guo, Na Xie, Song Zhou, Wu Zhaohui, Jie Mu, Hao Peng, and Feng Jing

Doc ID: 290776 Received 20 Mar 2017; Accepted 17 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We report on a multi-petawatt 3-cascaded all optical parametric chirped pulse amplification laser facility. The experimental results demonstrate that the maximum energy after the final amplifier and after the compressor is 168.7 J and 91.1 J respectively. The pulse width (FWHM) is 18.6 fs after optimization of pulse compression. Therefore, 4.9 PW peak power has been achieved for the laser facility. To the best of our knowledge, this is the highest pulse power reported so far for an all-OPCPA facility, and a compressed pulse shorter than 20 fs is achieved in a petawatt-class laser facility for the first time.

Enhanced performance in serial-to-parallel data conversion via Raman-assisted time lens processing

Junying Ru, Qijie Xie, Chaoran Huang, Bofang Zheng, and Chester C.T. Shu

Doc ID: 290920 Received 21 Mar 2017; Accepted 17 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We have demonstrated a new approach to enhance the uniformity of conversion efficiency in serial-to-parallel data conversion via time lens processing. In our approach, Raman amplification is applied to enhance four-wave mixing in a highly nonlinear fiber. By carefully selecting the pump wavelength, the Raman gain profile can be exploited to compensate the roll-off in conversion efficiency resulted from the varying phase mismatch between the linearly chirped pump and the signal. With Raman amplification, improvement of sensitivity up to 6.8 dB has been experimentally obtained. The variation of sensitivity across the output channels has been reduced from 8.4 to 2.0 dB.

A large-scale nanostructured low-temperature solar selective absorber

Kequn Chi, Liu Yang, Zhaolang Liu, Pingqi Gao, Jichun Ye, and Sailing He

Doc ID: 290704 Received 15 Mar 2017; Accepted 16 Apr 2017; Posted 17 Apr 2017  View: PDF

Abstract: A large-scale nanostructured low-temperature solar selective absorber is demonstrated experimentally. It consists of a silicon dioxide thin film coating on a rough refractory tantalum substrate, fabricated based simply on self-assembled closely-packed polystyrene nanospheres. Because of the strong light harvesting of the surface nanopatterns and constructive interference within the top silicon dioxide coating, our absorber has a much higher solar absorption (0.82) than its planar counterpart (0.68). Though its absorption is lower than that of commercial black paint with ultra-broad absorption, the greatly-suppressed absorption/emission in the long range still enables a superior heat accumulation. The working temperature is as high as 189.6 °C under 7-sun solar illumination in ambient conditions, much higher than those achieved by the two comparables. Therefore, our absorber is very promising in practical solar thermal applications.

Reconfigurable opto-thermal graded-index waveguiding in bulk chalcogenide glasses

Soroush Shabahang, Nicholas Nye, Christos Markos, Demetrios Christodoulides, and Ayman Abouraddy

Doc ID: 291220 Received 22 Mar 2017; Accepted 16 Apr 2017; Posted 17 Apr 2017  View: PDF

Abstract: In the absence of suitable deposition processes, the fabrication of graded-index chalcogenide waveguides or fibers remains an outstanding challenge. Here, by exploiting the strong thermo-optic effect present in chalcogenide glasses, we experimentally demonstrate non-permanent optically-induced waveguides in bulk As$_2$Se$_3$ rods using a 1.55-$\mu$m-wavelength laser. This single-step process can be used not only to self-trap the writing beam, but also to guide another optical beam at a different wavelength in the opto-thermally inscribed waveguide channel. These results could pave the way towards harnessing nonlinear effects in graded-index chalcogenide guided settings.

Surface enhanced infrared absorption of chemisorbed carbon monoxide using plasmonic nanoantennas

Johannes Haase, Salvatore Bagiante, Hans Sigg Hans Sigg, and Jeroen van Bokhoven

Doc ID: 290705 Received 17 Mar 2017; Accepted 14 Apr 2017; Posted 14 Apr 2017  View: PDF

Abstract: We report the enhancement of infrared absorption of chemisorbed carbon monoxide on platinum in the gap of plasmonic nanoantennas. Our method is based on the self-assembled formation of platinum nano islands on nanoscopic dipole antenna arrays manufactured via electron beam lithography. We employ systematic variations of the plasmonic antenna resonance to precisely couple to the molecular stretch vibration of carbon monoxide adsorbed on the platinum nano islands. Ultimately we reach more than 1500 fold infrared absorption enhancements allowing for an ultrasensitive detection of a monolayer of chemisorbed carbon monoxide. The developed procedure can be adapted to other metal adsorbents and other molecular species and could for instance be utilized for coverage sensing in surface catalytic reactions.

Non-Resonant Modes in Plasmonic Holey Metasurfaces for the Design of Artificial Flat Lenses

Guido Valerio, Zvonimir Sipus, Anthony Grbic, and Oscar Quevedo-Teruel

Doc ID: 291037 Received 22 Mar 2017; Accepted 14 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: This paper discusses non-resonant modes excited on holey metasurfaces, and their influence on the properties of spoof plasmonic states supported by the metasurface when a second surface is placed in its proximity. We consider here a metallic surface with periodic holes drilled in it. The field excited on each hole is projected onto a set of non-resonant modes in order to discuss their relative relevance. While previous simpler models were assuming only the presence of the fundamental mode, we show that the simultaneous presence of several modes occurs when the surface is placed next to a metallic plate. Therefore, higher-order modes are responsible for the peculiar physical properties of wave propagation of spoof plasmons between two surfaces, which can lead to new gradient-index flat lenses for transceivers for space communications.

Semitransparent and flexible perovskite solar cell with high visible transmittance based on ultrathin metallic electrodes

XiaLi Ou, Jing Feng, Ming Xv, and Hong-Bo Sun

Doc ID: 285326 Received 13 Feb 2017; Accepted 13 Apr 2017; Posted 14 Apr 2017  View: PDF

Abstract: Herein, we fabricated semitransparent and flexible indium-free perovskite solar cells (PeSCs) with high visible transmittance employing two kinds of composite ultrathin metallic electrodes, MoO₃/Au and MoO₃/Au/Ag/MoO₃/Alq₃, as bottom and top electrodes, respectively. These electrodes show superb electrical conductivity, excellent mechanical robustness and high optical transparency which are quite suitable for semitransparent and flexible PeSCs. An overall power conversion efficiency (PCE) of 6.96% and an average visible transmittance (AVT) of 18.16% in the wavelength range of 380-790 nm were achieved. Furthermore, the devices maintained 71% of its initial PCE after 1000 bending cycles with a bending radius of 4 mm.

Active modulation of the terahertz spectra radiated from two air plasmas

Ying Zhang, wenfeng sun, Xinke Wang, Jiasheng Ye, Shengfei Feng, Peng Han, and Yan Zhang

Doc ID: 286017 Received 02 Feb 2017; Accepted 12 Apr 2017; Posted 17 Apr 2017  View: PDF

Abstract: A simple and energy-saving method has been proposed to actively modulate the spectra of terahertz waves radiated from two serial plasmas, which uses the background light to generate one plasma to make full use of the energy of the femtosecond laser. With this method, the modulation of the central frequency, spectral bandwidth, spectral profile of the output terahertz waves have been observed. The shifting of the frequency split has been manipulated by changing the distance of the two serial plasmas. The manipulation results agree with the ones simulated by transition-Cherenkov model. This proposed method provides a useful tool for getting the modulated terahertz spectra that can be used in the terahertz remote sensing.

Photonics sensing at the thermodynamic limit

George Skolianos, Arushi Arora, Martin Bernier, and Michel Digonnet

Doc ID: 285312 Received 23 Jan 2017; Accepted 12 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We report a slow-light fiber Bragg grating strain sensor with a resolution limited by the extremely low thermodynamic phase fluctuations of the fiber. This was accomplished by using a short grating (4.5 mm) to enhance the thermal phase noise, an ultra-stable interrogation laser to lower the laser frequency noise, and a slow-light mode with a high group index (~533) tosuppress all other noise sources. We demonstrate that in a similar but longer grating (21 mm), phase noise is suppressed in inverse proportion to the square root of the length, in accord with theory, leading to a strain resolution as low as 130 fε/√Hz and a minimum detectable length of ~3x10-15 m at 1.5 kHz.

Asymmetric LMA rod-type fiber for enhanced higher order mode delocalization

Zeinab Sanjabi Eznaveh, Jose Antonio-Lopez, James Anderson, Axel Schulzgen, and Rodrigo Amezcua Correa

Doc ID: 286876 Received 16 Feb 2017; Accepted 12 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We present a novel design of micro-structured large pitch, large-mode-area (LMA) asymmetric rod-type fiber. By reducing the cladding symmetry through six high refractive index germanium-doped silica inclusions, the fiber features strong higher-order mode (HOM) delocalization leading to a potentially enhanced preferential gain for the fundamental mode in active fibers. In addition, high resolution spatially and spectrally (S2) resolved mode analysis measurements confirm HOM contributions below 1% and LP1m-like HOM contributions below the detection limit. This proposed fiber design enables single mode operation, with close to diffraction limited beam quality of M2 = 1.3 and an effective mode area of 2560 μm2 at 1064 nm. This design opens up new insights into mitigating the threshold-like onset of modal instabilities (MI) in high power fiber lasers and fiber amplifiers by efficiently suppressing LP11 modes.

Absolute non-invasive measurement of CO2 mole fraction emitted by E. coli and S. aureus using calibration-free 2f WMS applied to a 2004 nm VCSEL

Zarin S., Arup Chakraborty, and abhishek upadhyay

Doc ID: 281991 Received 23 Dec 2016; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We report the first demonstration of accurate real-time non-invasive measurement of the absolute cumulative mole fraction of metabolic carbon dioxide emitted by Escherichia coli and Staphylococcus aureus over a period of several hours of their life cycles using a recently-developed calibration-free wavelength modulation spectroscopy technique. A 1mW vertical cavity surface emitting laser is used to interrogate a single rotational vibrational absorption line of carbon dioxide at 2003.5 nm. The measurements are immune to laser intensity fluctuations due to variable optical coupling that is inevitable in such free-space coupled experiments that run over 10-18 hours. The cumulative carbon dioxide mole fraction follows the characteristic modified Gompertz model that is typical of bacterial growth in batch cultures. The various characteristics growth parameters are extracted from this curve. The technique can be readily extended to study multiple volatile organic compounds that bacteria are known to emit.

Cavity enhanced thermo-optic bistability and hysteresis in a graphene-on-Si₃N₄ ring resonator

Yun Gao, Wen Zhou, Xiankai Sun, Hon Tsang, and Chester C.T. Shu

Doc ID: 285801 Received 30 Jan 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: Cavity enhanced thermo-optic bistability is studied in a graphene-on-Si₃N₄ ring resonator. By engineering the coverage of monolayer graphene on top of the Si₃N₄ ring resonator, we observe a twofold enhancement in the thermo-optically induced resonance shift rate and 18-fold increase in the effective nonlinear refractive index compared with the devices without graphene. The thermo-optic hysteresis loop is also characterized in this hybrid structure, where the experimental results agree well with the theoretical calculations. This study paves the way for the design of graphene-on-Si₃N₄ based high-speed photodetectors, modulators, and devices for on-chip nonlinear optical applications.

High-reflectance magnetron sputtered Sc-based x-ray multilayer mirrors for the water window

Catherine Burcklen, Franck DELMOTTE, Evgueni Meltchakov, david DENNETIÈRE, Blandine CAPITANIO, DE ROSSI Sébastien, and Francois Polak

Doc ID: 286084 Received 17 Feb 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We present an experimental comparison of several Sc-based short period multilayer mirrors including Cr/Sc with B4C barrier layers and CrNx/Sc and we propose a new material combination that provides high reflectance in the water window domain. Multilayer samples with period thickness in the range 1.5 nm to 1.7 nm have been deposited by magnetron sputtering and characterized by x-ray reflectometry with a Cu-Kα source and with synchrotron radiation near the Sc-L2,3 edge. Best results are achieved by combining the nitridation of Cr layers and the addition of B4C barrier layers. Near normal incidence reflectance as high as % has been measured at photon energy of 397 eV. A simulation model of the multilayer structure is proposed and predicts that reflectance higher than 32% are achievable with CrNx/B4C/Sc mirrors.

Laguerre-Gaussian modal q-plates

Etienne Brasselet and Mushegh Rafayelyan

Doc ID: 287548 Received 27 Feb 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We propose space-variant uniaxial flat optical elements designed to generate pure Laguerre-Gaussian modes with arbitrary azimuthal and radial indices $l$ and $p$ by considering the fundamental case of an incident Gaussian beam. This is done via the combined use of the dynamic and the geometric phases. Optimal design protocol for the mode conversion efficiency is derived and the corresponding characteristics are given for $-6 \leq l \leq 6$ and $0 \leq p \leq 5$. The obtained ``modal q-plates' may find many applications whenever the radial degree of freedom of a light field is at play.

Absolute frequency measurements of CHF₃ Doppler-free ro-vibrational transitions at 8.6 µm

Gianluca Galzerano, Alessio Gambetta, Edoardo Vicentini, Yuchen Wang, Nicola Coluccelli, Eugenio Fasci, Livio Gianfrani, Antonio Castrillo, Valentina Di Sarno, Luigi Santamaria, Pasquale Maddaloni, Paolo De Natale, and Paolo Laporta

Doc ID: 287557 Received 27 Feb 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We report on absolute measurements of saturated-absorption line-centers frequencies of room-temperature trifluoromethane using a quantum cascade laser at 8.6 µm and the frequency modulation spectroscopy method. Absolute calibration of the laser frequency is obtained by direct comparison with a mid-infrared optical frequency comb synthesizer referenced to a rf Rb standard. Several sub-Doppler transitions falling in the υ₅ vibrational band are investigated at around 1158.9 cm^{-1} with a fractional frequency precision of 8.6x10^{-12} at 1-s integration time, limited by the Rb-clock stability. The demonstrated frequency uncertainty of 6.6x10^{-11} is mainly limited by the reproducibility of the frequency measurements.

Pulse picker for synchrotron radiation driven by surface acoustic wave

Simone Vadilonga, Ivo Zizak, Dmitry Roshchupkin, Andrei Petsiuk, Igor Dolbnya, Kawal Sawhney, and Alexei Erko

Doc ID: 290474 Received 23 Mar 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: A functional test for a pulse picker for synchrotron radiation was performed at Diamond Light Source. The purpose of a pulse picker is to select which pulse from the synchrotron hybrid mode bunch pattern reaches the experiment. In the present work, the Bragg reflection on a Si/B4C multilayer was modified using surface acoustic wave (SAW) trains. Diffraction on the SAW alters the direction of the X-rays and it can be used to modulate the intensity of the X-rays that reach the experimental chamber. Using electronic modulation of the SAW amplitude it is possible to obtain different scattering conditions for different X-ray pulses.To isolate the single bunch, the state of the SAW must be changed in the short time gap between the pulses.To achieve the necessary time resolution the measurements have been performed in conical diffraction geometry. The achieved time resolution was 120 ns.

Thermo-optic characteristic of DNA thin solid film and its application as a biocompatible optical fiber temperature sensor

Seongjin Hong, Woohyun Jung, Tavakol Nazari, Sanggwon Song, Kyunghwan Oh, Chai Quan, and Taeoh Kim

Doc ID: 290612 Received 15 Mar 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We report a unique thermo-optical characteristics of DNA-CTMA (DNA-Cetyl tri-methyl ammonium) thin solid film with a large negative thermo-optical coefficient of -3.4 10-4/˚C in the temperature range from 20 ~ 70˚C without any observable thermal hysteresis. By combining this thermo-optic DNA film and fiber optic multimode interference (MMI) device, we experimentally demonstrated a highly sensitive compact temperature sensor with a large spectral shift of 0.15nm/˚C. The fiber optic MMI device was a concatenated structure with single mode fiber (SMF)-coreless silica fiber (CSF)-single mode fiber (SMF) and the DNA-CTMA film was deposited on the CSF. The spectral shifts of the device in experiments were compared with beam propagation method, which showed a good agreement.

Second-harmonic focusing by nonlinear turbid medium via feedback-based wavefront shaping

Yanqi Qiao, Yajun Peng, Yuanlin Zheng, Fangwei Ye, and Xianfeng Chen

Doc ID: 291059 Received 22 Mar 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: Scattering has usually been considered detrimental for optical focusing or imaging. Recently, more and more research has shown that strongly scattering materials can be utilized to focus coherent light by controlling or shaping the incident light. Here, purposeful focusing of second-harmonic waves, which are generated and scattered from nonlinear turbid media via feedback-based wavefront shaping is presented. This work shows a flexible manipulation of both disordered linear and nonlinear scattering signals, indicating more controllable degrees of freedom for the description of turbid media. This technique also provides a possible way to an efficient transmission of nonlinear signal at a desired location in the form of a focal point or other patterns. With the combination of random nonlinear optics and wavefront shaping methods, more interesting applications can be expected in the future, such as nonlinear transmission matrix, multi-frequency imaging and phase-matching-free nonlinear optics.

Programmable controlled mode-locked fiber laser using a digital micromirror device

Wu Liu, Jintao Fan, Chen Xie, Youjian Song, CHENGLIN Gu, Lu Chai, Qingyue Wang, and Ming-lie Hu

Doc ID: 291531 Received 29 Mar 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: A digital micromirror device (DMD) based arbitrary spectrum amplitude shaper is incorporated into a large-mode-area photonic crystal fiber (LMA-PCF) laser cavity. The shaper acts as an in-cavity programmable filter and provides large tunable dispersion from normal to anomalous. As a result, mode-locking is achieved in different dispersion regimes. By programming different filter profiles on the DMD, the laser generates femtosecond pulse with tunable central wavelength and controllable bandwidth. Under conditions of suitable cavity dispersion and pump power, design-shaped spectra are directly obtained by varying the amplitude transfer function of the filter. The results show the versatility of the DMD based in-cavity filter for flexible control of the pulse dynamics in mode-locked fiber laser.

Mirrors with Inverse Offset-Dependent Focal Length for Multi-Pass Cavities

Sarper Ozharar and Alphan Sennaroglu

Doc ID: 286724 Received 16 Feb 2017; Accepted 11 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We present a novel multi-pass-cavity (MPC) design based on the use of a rotationally symmetric end mirror whose focal length varies inversely as the ray height from the optical axis. We provide a detailed discussion of how ray tracing can be done for this system and show with numerical simulations, that a very rich set of exotic spot patterns can be formed on the end mirrors. We further show a specific q-preserving configuration where the q-parameters of the input and output beam remain the same. Finally, we derive the polar form of the mirror surface profile that gives this offset-dependent focal length.

Demonstration of a highly efficient terahertz flat lens employing tri-layer metasurfaces

Chun-Chieh Chang, Daniel Headland, Derek abbott, Withawat Withayachumnankul, and Hou-Tong Chen

Doc ID: 285767 Received 30 Jan 2017; Accepted 11 Apr 2017; Posted 12 Apr 2017  View: PDF

Abstract: We demonstrate a terahertz flat lens based on tri-layermetasurfaces allowing for broadband linear polarization conversion, where the phase can be tuned through a full 2π range by tailoring the geometry of the subwavelength resonators. The lens functionality is realized by arranging these resonators to create a parabolic spatial phase profile. The fabricated 124 μm-thick device was characterized by scanning the beam profile and cross section, showing diffraction-limited focusing and an overall efficiency of ∼68% at the operating frequency of 400 GHz. This device has potential for applications in terahertz imaging and communications, as well as beam control in general.

Performance comparison of pseudo-inverse and maximum-likelihood estimators of Stokes parameters in the presence of Poisson noise for spherical design-based measurement structures

Francois Goudail

Doc ID: 291790 Received 30 Mar 2017; Accepted 11 Apr 2017; Posted 17 Apr 2017  View: PDF

Abstract: Estimation of the Stokes vector from N>4 intensity measurements is usually performed with the pseudo-inverse (PI) estimator, which is optimal when the noise that corrupts the measurements is additive and Gaussian. In the presence of Poisson shot noise, the maximum-likelihood (ML) estimator is different from the PI estimator, but is more complex to implement since it is not closed-form. We compare in this Letter the precisions obtained with the ML and the PI estimators in the presence of Poisson noise when using measurement structures based on spherical designs. We show that in this case, the gain in precision brought by the ML estimator is real but modest, so that in applications where processing speed is an issue, the PI estimator can be considered sufficient. This result is important in the choice of the inversion strategy for Stokes polarimetry.

Optical Nyquist pulse generation by using a dual-electrode Mach-Zehnder modulator

Nobuhide Yokota, Ryo Igarashi, and Hiroshi Yasaka

Doc ID: 290182 Received 09 Mar 2017; Accepted 11 Apr 2017; Posted 12 Apr 2017  View: PDF

Abstract: We demonstrate a simple and efficient optical Nyquist pulse generation by using a dual-electrode Mach-Zehnder modulator (MZM) driven by a combination of fundamental and second harmonic RF signals. The method is based on a raised-cosine-shaped time filter and time lens created in the MZM under operation conditions given by a simple equation. Optical Nyquist pulses with a roll-off factor of 0.52 and intrinsic conversion efficiency of 37% are experimentally confirmed. Numerical analyses indicate that the roll-off factor can be moderately controlled down to ~0.3 by increasing relative strength of fundamental RF signals.

Terahertz multilevel phase Fresnel lenses fabricated by laser patterning of silicon

Linas Minkevicius, Simonas Indrišiūnas, Ramūnas Šniaukas, Bogdan Voisiat, Vytautas Janonis, Vincas Tamošiūnas, Irmantas Kašalynas, Gediminas Račiukaitis, and Gintaras Valušis

Doc ID: 287646 Received 28 Feb 2017; Accepted 11 Apr 2017; Posted 12 Apr 2017  View: PDF

Abstract: Multilevel Phase Fresnel Lenses (MPFLs) with high numerical aperture (NA) for terahertz (THz) frequencies were developed. The components based on monocrystalline silicon wafer are prepared by patterning by a high-speed industrial-scale laser-direct-write (LDW) system. Two consistent series of the THz-MPFLs with number of subzones varying between 2 and 1643 and the focal length of 5 mm and 10 mm were produced employing inherent flexibility of the three-dimensional (3D) DLW fabrication process. The focusing performance was studied at the optimal 0.58 THz frequency using a Gaussian beam profile and scanning 2D intensity distribution with THz detector along the optical axis. The efficiency of THz-MPFL was found to be dependent of the number of subzones. The position and orientation angle of the patterned plane of the silicon wafer were considered to reduce the effect of standing waves formation in the experiment.

Highly scalable femtosecond coherent beam combining demonstrated with 19 fibers

LE DORTZ Jérémy, anke heilmann, Marie Antier, Jerome Bourderionnet, Christian Larat, Ihsan Fsaifes, Louis Daniault, severine bellanger, Christophe Simon-Boisson, Jean-Christophe Chanteloup, Eric Lallier, and Arnaud Brignon

Doc ID: 288010 Received 08 Mar 2017; Accepted 10 Apr 2017; Posted 12 Apr 2017  View: PDF

Abstract: Coherent beam combining in the femtosecond regime of a record number of 19 fibers is demonstrated. The interferometric phase measurement technique, particularly well-suited to phase-lock a very large number of fibers, is successfully demonstrated in the femtosecond regime. A servo-loop is implemented to control piezo-electric fiber stretchers for both phase and delay variations compensation. The residual phase errors are below λ/60 rms. Nearly 50 % of the total energy is contained in the far field central lobe. After compression we obtain a combined pulse width of 300 fs identical to the master oscillator pulse width.

Ultra-slow light propagation by self-induced transparency in ruby in the superhyperfine limit

Hans Riesen, Aleksander Rebane, Rajitha Rajan, Wayne Hutchison, Steffen Ganschow, and Alex Szabo

Doc ID: 285878 Received 01 Feb 2017; Accepted 10 Apr 2017; Posted 12 Apr 2017  View: PDF

Abstract: Self-induced transparency is reported for circularly polarized light in the R1(-3/2) line of 30 ppm ruby (α-Al2O3:Cr3+) at 1.7 K in a magnetic field of B||c=4.5 T. In such a field and temperature a 30 ppm ruby is in the so-called superhyperfine limit resulting in a long phase memory time, TM=50 μs, and a thousand-fold slower pulse propagation velocity of ~300 m/s was observed, compared to the ~300 km/s measured in the first observation of SIT ~50 year ago, that employed ruby with a 500 ppm chromium concentration in zero field and at 4.2 K. To date this is the slowest pulse propagation ever observed in a SIT experiment.

A Simple Effective Medium Approximation with Rayleigh Scattering

Ashfaqul Siraji and Yang Zhao

Doc ID: 290100 Received 09 Mar 2017; Accepted 10 Apr 2017; Posted 11 Apr 2017  View: PDF

Abstract: We present a simple analytical effective medium approximation (EMA) which can account for finite sized and interacting inclusions in the Rayleigh scattering regime. The polarizability of individual inclusion is calculated using the Mie solution and net polarizability is formed, leading to the effective parameters. The Mie coefficients are expanded into polynomials and curtailed to the sixth order which is accurate in the Rayleigh regime. Results obtained using the developed models are compared with experimental results and popular EMAs. The analytical formula outperforms other EMAs for large inclusion size, high filling factor and high relative refractive index.

Phaseless Incoherent Optical Frequency Domain Spectroscopy

Ziv Glasser, Gidon Zaychik, Rita Abramov, Daniel Gotliv, and Shmuel Sternklar

Doc ID: 286497 Received 13 Feb 2017; Accepted 10 Apr 2017; Posted 11 Apr 2017  View: PDF

Abstract: We describe a new technique for Incoherent Optical Frequency Domain Spectroscopy (I-OFDS), which does not require measurements of the RF phase spectrum in order to reconstruct the optical spectrum. It is based on the addition of either an optical or electronic reference line to the I-OFDS system. High accuracy (error < 1%) is predicted and achieved.

Thulium fiber pumped tunable Ho:CaF2 laser

Michal Nemec, Jan Sulc, Michal Jelinek, Vaclav Kubecek, Helena Jelinkova, Maxim Doroshenko, Olimkhon Alimov, V. Konushkin, Andrei Nakladov, and Vyacheslav Osiko

Doc ID: 286869 Received 16 Feb 2017; Accepted 10 Apr 2017; Posted 11 Apr 2017  View: PDF

Abstract: We report the first room-temperature operation of in-band pumped Ho:CaF2 laser. A set of Ho:CaF2 crystals various in holmium concentrations from 0.1 up to 2.5 %, synthesized using Bridgeman technique, was used for lasing and related spectroscopy investigation. Pulsed 1.94 µm thulium fiber laser system was used for Ho:CaF2 longitudinal pumping. For 1.5 % Ho:CaF2 the maximal wavelength tunability (from 2064 to 2115 nm) and output energy (1.4 mJ at 2087 nm for absorbed pumping energy 34 mJ) were obtained. Without the tuning element the slope efficiency up to 30 % in respect to absorbed power was obtained using this sample.

Direct Stabilization of Optomechanical Oscillators

Ke Huang and Mani Hossein-Zadeh

Doc ID: 286974 Received 16 Mar 2017; Accepted 10 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We demonstrate a simple and effective technique for stabilizing the oscillation amplitude of a radiation pressure driven optomechanical RF oscillator (OMO). By controlling the optomechanical gain through a feedback loop that uses the oscillation amplitude itself as the feedback parameter, we have been able to suppress the amplitude fluctuations and drift. In contrast to more complex techniques that only fix the relative wavelength detuning, the proposed technique isolates the oscillation amplitude not only from laser wavelength variations but also laser power variations, ambient temperature variations and coupling gap variations. The amplitude stabilization also improves the stability of the oscillation frequency (compared to free running OMOs).

Self-compression of femtosecond deep-ultraviolet pulses by filamentation in krypton

Shunsuke Adachi and Toshinori Suzuki

Doc ID: 287380 Received 23 Feb 2017; Accepted 10 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We demonstrate self-compression of deep-ultraviolet (DUV) pulses by filamentation in krypton. In contrast to self-compression in the near-infrared, that in the DUV is associated with a red-shifted leading edge appearing in the pulse temporal profile. The achieved pulse width of 15 fs is the shortest among demonstrated sub-mJ deep-ultraviolet pulses.

Image recovery from defocused 2D fluorescent images in multimodal digital holographic microscopy

Xiangyu Quan, Osamu Matoba, and Yasuhiro Awatsuji

Doc ID: 286826 Received 21 Feb 2017; Accepted 09 Apr 2017; Posted 10 Apr 2017  View: PDF

Abstract: A technique of three-dimensional (3D) intensity retrieval from defocused, two-dimensional (2D) fluorescent images in the multimodal digital holographic microscopy (DHM) is proposed. In the multimodal DHM, 3D phase and 2D fluorescence distributions are obtained simultaneously by an integrated system of an off-axis DHM and a conventional epifluorescence microscopy, respectively. This gives us more information of the target, however, defocused fluorescent images are observed due to the short depth of field. In this Letter, we propose a method to recover the defocused images based on the phase compensation and backpropagation from the defocused plane to the focused plane by using the distance information that is obtained from the off-axis DHM. By applying Zernike polynomial phase correction, we brought back the fluorescent intensity to the focused imaging planes. The experimental demonstration using fluorescent beads is presented, and the expected applications are suggested.

Speckle-based hyperspectral imaging combining multiple scattering and compressive sensing in nanowire mats

Rebecca French, Sylvain Gigan, and Otto Muskens

Doc ID: 287330 Received 23 Feb 2017; Accepted 09 Apr 2017; Posted 10 Apr 2017  View: PDF

Abstract: Encoding of spectral information onto monochrome imaging cameras is of interest for wavelength multiplexing and hyperspectral imaging applications. Here, the complex spatio-spectral response of a disordered material is used to demonstrate retrieval of a number of discrete wavelengths over a wide spectral range. Strong, diffuse light scattering in a semiconductor nanowire mat is used to achieve a highly compact spectrometer of micrometer thickness, transforming different wavelengths into distinct speckle patterns with nanometer sensitivity. Spatial multiplexing is achieved through the use of a microlens array, allowing simultaneous imaging of many speckles, ultimately limited by the size of the diffuse spot area. The performance of different information retrieval algorithms is compared. A compressive sensing algorithm exhibits efficient reconstruction capability in noisy environments and with only a few measurements.

Origin and suppression of parasitic signals in Kagomé lattice hollow core fiber used for SRS microscopy and endoscopy

Alberto Lombardini, Esben Andresen, Alexandre Kudlinski, Ingo Rimke, and Herve Rigneault

Doc ID: 287373 Received 23 Feb 2017; Accepted 09 Apr 2017; Posted 10 Apr 2017  View: PDF

Abstract: Hollow core fibers are considered as promising candidates to deliver intense temporally overlapping picosecond pulses in applications such as stimulated Raman scattering (SRS) microscopy and endoscopy because of their inherent low nonlinearity compared to solid-core silica fibers. Here we demonstratethat—contrary to prior assumptions— parasitic signals are generated in Kagomé-lattice hollow core fibers.We identify the origin of the parasitic signals as an interplay between the Kerr nonlinearity of air and frequency dependent fiber losses. Importantly, we identify the special cases of experimental parameters that are free from parasitic signals making hollow core fibers ideal candidates for noise free SRS microscopyand endoscopy.

Designing ultrabroadband absorbers/emitters based on Bloch theorem and optical topological transition

Yinhui Kan, Changying Zhao, Xing Fang, and Boxiang Wang

Doc ID: 288035 Received 06 Mar 2017; Accepted 09 Apr 2017; Posted 12 Apr 2017  View: PDF

Abstract: In this paper, we propose a method to design ultrabroadband near-perfect absorbers/emitters, consisting of periodic dielectric-metal multilayer. In the method, Bloch theorem and optical topological transition (OTT) of isofrequency surfaces are employed to manipulate the starting and end of near-perfect spectral absorption band, respectively. Moreover, we design and fabricate an ultrabroadband near-perfect absorber utilizing the proposed method. The average absorption of the designed absorber is ~95% in the focused visible and near-infrared range (0.4-2 μm). This omnidirectional and polarization-independent near-perfect absorber ispromising for solar energy harvesting, emissivity control and thermal imaging.

Uncloaking diffusive-light invisibility cloaks by speckle analysis

Andreas Niemeyer, Frederik Mayer, Andreas Naber, Milan Koirala, Alexey Yamilov, and Martin Wegener

Doc ID: 285550 Received 25 Jan 2017; Accepted 08 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: Within the range of validity of the stationary diffusion equation, an ideal diffusive-light invisibility cloak can make an arbitrary macroscopic object hidden inside of the cloak indistinguishable from the surrounding for all colors, polarizations, and directions of incident visible light. However, the diffusion equation for light is an approximation which becomes exact only in the limit of small coherence length. Thus, one expects that the cloak can be revealed by illumination with coherent light. The experiments presented here show that the cloaks are robust in the limit of large coherence length but can be revealed by analysis of the speckle patterns under illumination with partially coherent light. Experiments on cylindrical core-shell cloaks and corresponding theory are in good agreement.

Multiple wavelength DFB laser arrays with high coupling coefficient and precise channel spacing

Song Tang, Lianping Hou, Xiangfei Chen, and John Marsh

Doc ID: 286963 Received 17 Feb 2017; Accepted 08 Apr 2017; Posted 10 Apr 2017  View: PDF

Abstract: Special designs of sampled Bragg gratings have been used to fabricate distributed feedback semiconductor laser arrays with very precise wavelength spacing and strong coupling coefficients. By dividing one sampling period into two equal sections, each with a grating but with a π-phase shift between the sections, the ±1st-order channels are enhanced while eliminating the 0th-order reflection. By using multiple phase-shifted sections, only the −1st-order channel is enhanced. Using a single electron beam lithography step and two π-phase shifted sections, we have fabricated an eight-channel laser array with channel spacing of 100 GHz.

On the cancellation of OAM beams propagating through convective turbulence

Gustavo Funes and Jaime Anguita

Doc ID: 287671 Received 01 Mar 2017; Accepted 07 Apr 2017; Posted 10 Apr 2017  View: PDF

Abstract: By means of an experimental setup, we study the time evolution of orbital angular momentum (OAM) crosstalk after a five-meter propagation path with a turbulence perturbation generated by a flat heater. This convective turbulence could simulate the beam passing over hot concrete or building roofs. We study the consequences of using a wide range of transmission OAM states. We also explore the effect of misalignment, and we propose two new different techniques for analyzing the vortex cancellation. Even though results are inconsistent with theoretical predictions, specially for low turbulence regimes, we state that signal to noise ratio is the key factor to understand this discrepancy. Finally, a crosstalk correction method is proposed via image post-processing that would open the possibility of an adaptive optics approach that is different from conventional ones.

Nanofilm-induced spectral tuning of third harmonic generation

Stephen Warren-Smith, Mario Chemnitz, Henrik Schneidewind, Roman Kostecki, Heike Ebendorff-Heidepriem, Tanya Monro, and Markus Schmidt

Doc ID: 286308 Received 07 Feb 2017; Accepted 07 Apr 2017; Posted 07 Apr 2017  View: PDF

Abstract: Intermodal third-harmonic generation using waveguides is an effective frequency conversion process due to the combination of long interaction lengths and strong modal confinement. Here we introduce the concept of tuning the third harmonic phase-matching condition via the use of dielectric nanofilms located on an open waveguide core. We experimentally demonstrate that tantalum oxide nanofilms coated onto the core of an exposed core fiber allow tuning the third harmonic wavelength over 30 nm, as confirmed by qualitative simulations. Due to its generic character, the presented tuning scheme can be applied to any form of exposed core waveguide and will find applications in fields including microscopy, biosensing, and quantum optics.

Depth-resolution enhancement of terahertz deconvolution by autoregressive spectral extrapolation

Junliang Dong, Alexandre Locquet, and David Citrin

Doc ID: 287452 Received 27 Feb 2017; Accepted 07 Apr 2017; Posted 11 Apr 2017  View: PDF

Abstract: This Letter presents a method for enhancing the depth-resolutionof terahertz deconvolution based on autoregressive spectral extrapolation. The terahertz frequency components with high signal-to-noise ratioare modeled with an autoregressive process, and the missing frequency components in the regions with low signal-to-noise ratio are extrapolated based on the autoregressive model. In this way, the entire terahertz frequency spectrum of the impulse response function, corresponding to the material structure, is recovered. This method, which is verified numerically and experimentally, is able to provide a ’quasi-ideal’ impulse response function, and therefore, greatly enhances the depth-resolution for characterizing optically thin layers in the terahertz regime.

Estimation of photonic crystal fiber dispersion by means of supercontinuum generation

Julius Vengelis, Vygandas Jarutis, and Valdas Sirutkaitis

Doc ID: 290982 Received 21 Mar 2017; Accepted 06 Apr 2017; Posted 10 Apr 2017  View: PDF

Abstract: We present a novel technique for photonic crystal fiber dispersion measurement. We demonstrate that investigating supercontinuum using cross-correlation frequency resolved optical gating (XFROG) technique can be used as a novel method for quantitatively characterizing dispersion and observing orthogonal polarization modes in polarization maintaining photonic crystal fibers. XFROG trace of supercontinuum reveals complex behavior of orthogonal polarization modes which is different in normal and anomalous dispersion regions of the photonic crystal fiber.

Correlation and squeezing for optical transistor and intensity router applications in Diamond NV Center.

Noor Ahmed, GHULAM KHAN, Ruimin Wang, JINGRU HOU, RUI GONG, LINGMENG YANG, and Yanpeng Zhang

Doc ID: 290324 Received 09 Mar 2017; Accepted 06 Apr 2017; Posted 06 Apr 2017  View: PDF

Abstract: We study an optical transistor (switch and amplifier) and router by spontaneous parametric four-wave mixing and fluorescence in two and V-type level system of diamond NV center. The routing results from three peaks of Fluorescence signal in time domain, while the switching and amplification are realized by correlation and squeezing. Moreover, the control mechanism of optical transistor and router has been configured using the power of the incident beams. The results are applicable to all optical switching and routing.

Resolving 1 million sensing points in an optimized differential time-domain Brillouin sensor

Alejandro Dominguez-Lopez, Marcelo Soto, Sonia Martin-Lopez, Luc Thevenaz, and Miguel Gonzalez Herraez

Doc ID: 284561 Received 19 Jan 2017; Accepted 06 Apr 2017; Posted 07 Apr 2017  View: PDF

Abstract: A differential pulse-width pair (DPP) Brillouin distributed fiber sensor is implemented to achieve centimetric spatial resolution over distances of several kilometers. The presented scheme uses a scanning method in which the spectral separation between the two probe sidebands is kept constant, while the optical frequency of the pump is swept to scan the Brillouin spectral response. Experimental results show that this method avoids detrimental temporal distortions of the pump pulses, which in a standard implementation prevents the DPP method to operate over mid-to-long distances. Such novel scanning procedure allows resolving, for the first time in pure time-domain Brillouin sensors, 1’000’000 sensing points, i.e., 1 cm spatial resolution over 10 km in a conventional acquisition time.

Are optical fibers really uniform? Measurement of refractive index on a centimeter scale

Sébastien Loranger and Raman Kashyap

Doc ID: 287461 Received 27 Feb 2017; Accepted 05 Apr 2017; Posted 10 Apr 2017  View: PDF

Abstract: Many applications of optical fiber, such as specialized fiber Bragg gratings (FBG) require high uniformity of a fiber’s refractive index (RI) along its length. We show here that the mode effective index of most fibers is not constant even on a short length scale. To help improve fiber manufacturing and selection, we demonstrate a technique for characterizing meter length single-mode optical fiber’s effective RI over a cm-scale with a precision of 3 x 10-6 RI units (RIU) and an absolute accuracy of 2 x 10-4 RIU. By writing several weak probe fiber Bragg gratings (FBGs) as frequency references and then measuring the frequency deviation of these probe FBGs along the length of the fiber with an optical Fourier domain reflectometer, the RI distribution of the effective mode index may be found. We validate our measurements on reference and fibers under test with theoretical simulations.

Fabrication of Multi-point Side-Firing Optical Fiber by Laser Micro-ablation

Hoang Nguyen, arnob masud, Aaron Becker, John Wolfe, Matthew Hogan, Philip Horner, and Wei-chuan Shih

Doc ID: 286622 Received 23 Feb 2017; Accepted 05 Apr 2017; Posted 07 Apr 2017  View: PDF

Abstract: A multi-point, side-firing design enables an optical fiber to output light at multiple desired locations along the fiber body. This provides advantages over end-to-end traditional fibers, especially in applications requiring fiber bundles such as brain stimulation or remote sensing. This paper demonstrates that continuous wave (CW) laser micro-ablation can controllably create conical-shaped cavities, or side windows, for outputting light. The dimensions of these cavities determine the amount of photons released and their exit angle. Experimental data show that a single side window on a 730 μm fiber can deliver more than 8 % of the input light. This was increased to more than 19 % on a 65 µm fiber with side windows created using femtosecond (fs) laser ablation and chemical etching. Fine control of light distribution along an optical fiber is critical for various biomedical applications such as light activated drug-release and optogenetics studies.

Modal interferometer based in a single mechanically-induced long-period fiber grating and a nanoparticles-coated film section

Karla Salas-Alcántara, Laura Aparicio-Ixta, Ismael Torres-Gomez, Mario-Alejandro Rodríguez-Rivera, Gabriel Ramos-Ortiz, Rafael Espinosa Luna, and Juan PIchardo-Molina

Doc ID: 286658 Received 15 Feb 2017; Accepted 05 Apr 2017; Posted 07 Apr 2017  View: PDF

Abstract: A modal interferometer by a single mechanically-induced long-period grating (MI-LPFG) using a half-length coating fiber is presented. The coating material used for this work is a film of silica nanoparticles doped with an organic chromophore. The silica nanoparticles, with a diameter within the range of 40-50 nm, were deposited over 3.5 cm length of fiber by the dip-coating method, forming a film with a thickness between 500 and 1250 nm. Then the modal interferometer was implemented by inscribing the MI-LPFG over the coated fiber section and a similar fiber length of the uncoated fiber. The experimental results show high-contrast transmission bands, where the position and depth of the absorption envelope band is finely selected by the grating period, the pressure applied, and the film thickness. The novel modal interferometer architecture based on a single MI-LPFG combined with a functionalized-nanoparticles coating film offers an attractive platform for the development of fiber sensors and other fiber-based devices.

Pilot-tone based self-homodyne detection using optical nonlinear wave mixing

Yinwen Cao, Morteza Ziyadi, Ahmed Almaiman, Amirhossein Mohajerin Ariaei, Peicheng Liao, Changjing Bao, Fatemeh Alishahi, Ahmad Fallahpour, Bishara Shamee, Asher Willner, Youichi Akasaka, Tadashi Ikeuchi, Steven Wilkinson, Carsten Langrock, Martin Fejer, Joseph Touch, Moshe Tur, and Alan Willner

Doc ID: 287889 Received 13 Mar 2017; Accepted 04 Apr 2017; Posted 11 Apr 2017  View: PDF

Abstract: An all-optical pilot-tone based self-homodyne detection scheme using nonlinear wave mixing is experimentally demonstrated. Two scenarios are investigated using (i) multiple WDM channels with sufficient power of pilot tones, (ii) a single channel with a low-power pilot tone. The eye-diagram and bit-error-rate (BER) of the system are studied by tuning various parameters, such as pump power, relative phase, and pilot-to-signal ratio (PSR).

Cryogenically cooled CeF3 crystal as media for high power magnetooptical devices

Alexey Starobor, Evgeniy Mironov, Ilya Snetkov, Oleg Palashov, Hiroaki Furuse, Shigeki Tokita, and Ryo Yasuhara

Doc ID: 285948 Received 31 Jan 2017; Accepted 03 Apr 2017; Posted 04 Apr 2017  View: PDF

Abstract: The thermally induced depolarization and Verdet constant of CeF3 crystals that are their most important characteristics have been studied in the 79-293 К temperature range. It has been found that thermal effects reduce substantially on cooling down to 79 K and Verdet constant grows in inverse proportion to temperature. It was shown that CeF3 crystals are not inferior to TGG as a medium for Faraday isolators, including cryogenic ones.

Adding a spin to Kerker's condition: angular tuning of directional scattering with designed excitation

Lei Wei, Nandini Bhattacharya, and H. Urbach

Doc ID: 291266 Received 23 Mar 2017; Accepted 03 Apr 2017; Posted 04 Apr 2017  View: PDF

Abstract: We describe a method to control the directional scattering of a high index dielectric nanosphere, which utilizes the unique focusing properties of an azimuthally polarized phase vortex and a radially polarized beam to independently excite inside the nanosphere a spinning magnetic dipole and a linearly polarized electric dipole mode normal to the magnetic dipole. We show that by simply adjusting the phase and amplitude of the field on the exit pupil of the optical system, the scattering of the nanosphere can be tuned to any direction within a plane and the method works over a broad wavelength range.

Three-dimensional electromagnetic Gaussian Schell-model sources

Olga Korotkova, Lutful Ahad, and Tero Setala

Doc ID: 287528 Received 27 Feb 2017; Accepted 03 Apr 2017; Posted 05 Apr 2017  View: PDF

Abstract: We introduce three-dimensional (3D), stationary, electromagnetic Gaussian Schell-model (GSM) sources in the space-frequency domain and derive the realizability conditions that the source parameters must obey. In particular, we extend to 3D GSM sources two approaches to the realizability conditions presented previously for beam-like GSM sources. The results are of interest in the analysis and synthesis of tunable nonparaxial, partially coherent, partially polarized light fields.

Spectral selectivity in capillary dye lasers

Esmaeil Mobini, Behnam Abaie, Mostafa Peysokhan, and Arash Mafi

Doc ID: 287885 Received 02 Mar 2017; Accepted 31 Mar 2017; Posted 05 Apr 2017  View: PDF

Abstract: We explore the spectral properties of a capillary dye laser in the highly multimode regime. Our experiments indicate that the spectral behavior of the laser does not conform with a simple Fabry-Perot analysis; rather, it is strongly dictated by a Vernier resonant mechanism involving multiple modes, which propagate with different group velocities. The laser operates over a very broad spectral range and the Vernier effect gives rise to a free spectral range which is orders of magnitude larger than that expected from a simple Fabry-Perot mechanism. The presented theoretical calculations confirm the experimental results. Propagating modes of the capillary fiber are calculated using the finite element method (FEM) and it is shown that the optical pathlengths resulting from simultaneous beatings of these modes are in close agreement with the optical pathlengths directly extracted from the Fourier Transform of the experimentally measured laser emission spectra.

Wavelength Division Multiplexed Light Source Monolithically Integrated on a Silicon Photonics Platform

Purnawirman Purnawirman, Nanxi Li, Emir Magden, Gurpreet Singh, Michele Moresco, Thomas Adam, Gerald Leake, Douglas Coolbaugh, Jonathan Bradley, and Michael Watts

Doc ID: 287189 Received 23 Feb 2017; Accepted 31 Mar 2017; Posted 07 Apr 2017  View: PDF

Abstract: We demonstrate monolithic integration of a wavelength division multiplexed (WDM) light source for silicon photonics by cascade of erbium doped aluminum oxide (Al2O3: Er3+) distributed feedback (DFB) lasers. Four DFB lasers with uniformly spaced emission wavelengths are cascaded in series to simultaneously operate with no additional tuning required. A total output power of −10.9 dBm is obtained from the four DFBs with an average side mode suppression ratio (SMSR) of 38.1 ± 2.5 dB. We characterize the temperature dependent wavelength shift of the cascaded-DFBs and observe a uniform dλ/dT of 0.02 nm/oC across all four lasers.

Laser waveform control of extreme ultraviolet high harmonics from solids

Yongsing You, mengxi wu, Yanchun Yin, Andrew Chew, Xiaoming Ren, Shima Gholam Mirzaeimoghadar, Dana BROWNE, Michael Chini, Zenghu Chang, Kenneth Schafer, Mette Gaarde, and Shambhu Ghimire

Doc ID: 285934 Received 02 Feb 2017; Accepted 28 Mar 2017; Posted 03 Apr 2017  View: PDF

Abstract: Solid-state high harmonic sources offer the possibility of compact, high repetition rate attosecond light emitters. However, the time structure of high harmonics must be characterized at the sub-cycle level. We use strong two-cycle laser pulses to directly control the time-dependent nonlinear current in single crystal MgO leading to generation of extreme ultraviolet harmonics. We find that harmonics are delayed with respect to each other, yielding an atto-chirp, the value of which depends on the laser field strength. Our results provide the foundation for attosecond pulse metrology based on solid-state harmonics and a new approach to study sub-cycle dynamics in solids.

Light field endoscopy and its parametric discription

Jingdan Liu, Daniel Claus, Tingfa Xu, Thorben Kessner, Alois Herkommer, and Wolfgang Osten

Doc ID: 276210 Received 21 Sep 2016; Accepted 27 Mar 2017; Posted 06 Apr 2017  View: PDF

Abstract: In this letter we demonstrate the application of light field imaging to endoscopy. By introducing a microlens array into the image plane of a conventional endoscope, the 4D light field can be captured in one snapshot. This information can be used to obtain perspective images and to digitally refocus to different planes. These features allow for the recovery of three dimensional information in minimally invasive surgery. Important optical setup and performance parameters are derived to enable task specific engineering of the light field imaging system.

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