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Experimental demonstration of apodized-imaging chip-fiber grating coupler for Si3N4 waveguides

Yang Chen, Thalía Domínguez Bucio, Ali Khokhar, MEHDI BANAKAR, Katarzyna Grabska, Frederic Gardes, Robert Halir, I. Molina-Fernández, Pavel Cheben, and Jian-Jun He

Doc ID: 298179 Received 16 Jun 2017; Accepted 17 Aug 2017; Posted 17 Aug 2017  View: PDF

Abstract: Silicon nitride waveguide is a promising platform for integrated photonics, particularly due to its low propagation loss compared to other CMOS compatible waveguides, including silicon-on-insulator. Input/output coupling in such thin optical waveguides is a key issue for practical implementations. Fiber-to-chip grating couplers in silicon nitride usually exhibit low coupling efficiency, because the moderate index contrast leads to weak radiation strengths and poor directionality. Here, we present the first experimental demonstration of a recently proposed apodized-imaging fiber-to-chip grating coupler in silicon nitride that images an in-plane waveguide mode to an optical fiber placed at a specific distance above the chip. By employing amplitude and phase apodization, the diffracted optical field of the grating is matched to the fiber mode. High grating directionality is achieved by using stair-case grating teeth which produce a blazing effect. Experimental results demonstrate an apodized-imaging grating coupler with a record coupling efficiency of -1.5dB and a 3dB bandwidth of 60nm in the C-band.

Continuous-wave optically pumped green perovskite vertical-cavity surface-emitter

Mohammed Sharizal, zhixiong liu, abdullah al-atawi, Tien Khee Ng, Tom Wu, and Boon Ooi

Doc ID: 303290 Received 28 Jul 2017; Accepted 17 Aug 2017; Posted 17 Aug 2017  View: PDF

Abstract: We report an optically pumped green perovskite vertical-cavity surface-emitter operating in continuous wave (CW) at room temperature with a power density threshold of ~89 kW/cm². The device has an active region of CH₃NH₃PbBr₃ embedded in a dielectric microcavity and its feat was achieved with a combination of optimal spectral alignment of the optical cavity modes with the perovskite optical gain, an adequate Q-factor of the microcavity, adequate thermal stability, and improved material quality with a smooth, passivated, and annealed thin active layer. Our results signify a way towards CW perovskite emitters operation and electrical injection using low-cost fabrication methods for addressing monolithic optoelectronic integration and lasing in the green-gap.

Experimental generation of discrete ultraviolet wavelength by cascaded intermodal four-wave mixing in a multimode photonic crystal fiber

Jinhui Yuan, Zhe Kang, Feng Li, Xianting Zhang, Chao Mei, Guiyao Zhou, Xinzhu Sang, Qiang Wu, Binbin Yan, Xian Zhou, Kang Ping Zhong, Kuiru Wang, Chongxiu Yu, Gerald Farrell, Chao Lu, Hwa Yaw Tam, and Ping Kong Wai

Doc ID: 303460 Received 27 Jul 2017; Accepted 16 Aug 2017; Posted 17 Aug 2017  View: PDF

Abstract: Intermodal four-wave mixing (FWM) as one of nonlinear spatiotemporal effects in multimode optical fibers can be exploited to convert the available laser pump energy to the desired spectral regions. In this letter, we experimentally demonstrated discrete ultraviolet (UV) wavelength generations by cascaded intermodal FWM for the first time when femtosecond pump pulses at 800 nm are launched into the deeply normal dispersion region of the fundamental guided-mode of a multimode photonic crystal fiber (MPCF). For pump pulses with average input powers Pav=450, 550, and 650 mW, the first anti-Stokes waves are efficiently generated at the visible wavelength of 538.1 nm through intermodal phase-matching between the fundamental and second-order guided-modes of the MPCF. Then the first anti-Stokes waves generated serve as the secondary pump for the next intermodal FWM process. The second anti-Stokes waves in the form of the third-order guided-mode are generated at the UV wavelength of 375.8 nm. The maximum output power is above 10 mW for Pav=650 mW. We also confirm that the influences of fiber bending and intermodal walk-offs on the proposed cascaded intermodal FWM-based frequency conversion process are very small.

Pump-degenerate phase-sensitive amplification in amorphous silicon waveguides

Amy Foster, Ke-Yao Wang, and Hongcheng Sun

Doc ID: 300922 Received 27 Jun 2017; Accepted 16 Aug 2017; Posted 16 Aug 2017  View: PDF

Abstract: We demonstrate phase-sensitive amplification in hydrogenated amorphous silicon photonic waveguides based on pump-degenerate four-wave mixing at repetition rates of both 90 MHz and 10 GHz. At 90-MHz pulsed operation, an 11.7-dB phase-sensitive extinction ratio is achieved with a peak pump power of 1.6 W. At 10-GHz pulsed operation, a 6.6-dB phase-sensitive extinction ratio is achieved with a peak pump power of 0.5 W.

Linearly polarized cascaded Raman fiber laser with random distributed feedback operating beyond 1.5 µm

Ivan Lobach, Sergey Kablukov, and Sergey Babin

Doc ID: 301352 Received 29 Jun 2017; Accepted 15 Aug 2017; Posted 16 Aug 2017  View: PDF

Abstract: We report on the first demonstration of a linearly-polarized cascaded Raman fiber laser based on a simple half-open cavity with a broadband composite reflector and random distributed feedback in a polarization-maintaining phosphosilicate fiber with zero dispersion wavelength at ~1400 nm. Pumped by a 1080-nm Yb-doped fiber laser, the random laser delivers more than 8 W at 1262 nm and 9 W at 1515 nm with polarization extinction ratio of 27 dB. The generation linewidths amount to about 1 nm and 3 nm, respectively, being almost independent of power, in correspondence with the theory of a cascaded random fiber lasing.

Mixture fraction imaging at 1 kHz using femtosecond laser-induced fluorescence of krypton

Daniel Richardson, Naibo Jiang, Hans Stauffer, Sean Kearney, Sukesh Roy, and James Gord

Doc ID: 302384 Received 17 Jul 2017; Accepted 14 Aug 2017; Posted 15 Aug 2017  View: PDF

Abstract: Femtosecond (fs), two-photon-absorption laser-induced-fluorescence (TALIF) imaging measurements of krypton (Kr) are demonstrated to study mixing in gaseous flows. A measurement approach is presented in which observed Kr TALIF signals are seven times stronger than the current state-of-the-art methodology. Fluorescence emission is compared for different gas pressures and excitation wavelengths and the strongest fluorescence signals were observed when the excitation wavelength was tuned to 212.56 nm. Using this optimized excitation scheme, 1-kHz, single-laser-shot visualizations of unsteady flows and two-dimensional measurements of mixture fraction and scalar dissipation rate of a Kr-seeded jet are demonstrated.

Rapid measurement of transversal flow velocity vector with high spatial resolution using speckle decorrelation optical coherence tomography

Lei Fu, Ya Su, Yimin Wang, Lei Chen, wenping li, hongjie wang, Zhi Hong Li, and Steve Yao

Doc ID: 302724 Received 18 Jul 2017; Accepted 14 Aug 2017; Posted 15 Aug 2017  View: PDF

Abstract: We propose and demonstrate a novel method which uses only 3 sets of B-scans to accurately determine both the direction and the speed of a transversal flow using Speckle Decorrelation Optical Coherence Tomography (OCT). Our tri-scan method has the advantages of high measurement speed, high spatial resolution, and insensitivity to the flow speed. By introducing error maps, we show that the flow angle inaccuracy can be minimized by choosing the measurement result with a lesser error between results obtained from the x- and y-scans. Finally, we demonstrate that the flow angle measurement accuracy can be further improved for the high speed flows by increasing the speed of the x- and y-scans. © 2017 Optical Society of America

Large-bandwidth, low-loss, efficient mode mixing using long-period mechanical gratings

Bin Huang, Haoshuo Chen, Nicolas Fontaine, Roland Ryf, Ian Giles, and Guifang Li

Doc ID: 303313 Received 28 Jul 2017; Accepted 13 Aug 2017; Posted 17 Aug 2017  View: PDF

Abstract: We propose a new architecture for using long-period fiber grating (LPG) to induce strong mode mixing with low loss for space-division multiplexing. In this architecture, LPGs are installed in step-index few-mode fibers that support more modes than the transmission fiber. Such a design could significantly reduce losses due to coupling from the highest-order mode group to cladding modes. In our experiment, efficient mixing of three spatial modes over a broad bandwidth was achieved by a mechanical long-period grating on a step-index fiber that supports eight spatial modes. The insertion loss including two splice losses is less than 0.5dB and the coupling matrix and mode dependent loss are characterized experimentally for the first time. Strong mixing between LP01 and LP11 for whole C band is demonstrated and mode depend loss introduced to the system is negligible.

Development of an atmospheric polarization Scheimpflug lidar system based on a time-division multiplexing scheme

Liang Mei and Peng Guan

Doc ID: 302415 Received 14 Jul 2017; Accepted 12 Aug 2017; Posted 17 Aug 2017  View: PDF

Abstract: A polarization Scheimpflug lidar system based on the Scheimpflug principle has been developed by employing two linearly polarized 808-nm laser diodes and a CMOS image sensor. The polarization of one laser diode is rotated 90° by a half-wave plate. The two laser beams with orthogonal polarizations are combined by a polarization beam splitter, and then transmitted into atmosphere. The corresponding parallel and perpendicular polarized backscattering echoes are detected by the 45° tilted CMOS sensor using a time-division multiplexing scheme. 24-hour continuous atmospheric vertical profiling of depolarization ratio has been performed by using the polarization Scheimpflug lidar system. The promising results successfully demonstrated that the present lidar system has a great potential for the polarization studies of atmospheric aerosols.

Secure communication systems based on chaos in optically-pumped spin-VCSELs

Nianqiang Li, Hadi Susanto, Ben Cemlyn, Ian Henning, and Michael Adams

Doc ID: 301827 Received 05 Jul 2017; Accepted 11 Aug 2017; Posted 16 Aug 2017  View: PDF

Abstract: We report on a master and slave configuration consisting of two optically-pumped spin vertical-cavity surface-emitting lasers (VCSELs) for chaos synchronization and secure communication. Under appropriate conditions, high-quality chaos synchronization is achieved. We propose two encryption schemes, where either the pump magnitude or polarization is modulated. The results show that these allow for Gb/s transmission of secure data but exhibit different features: one indicates the message can be recovered by the total intensity but not the polarization components, whereas the other shows that the message can be better or exclusively retrieved from the polarization components at high bit rates.

Interaction of surface plasmon polaritons and acoustic waves inside an acoustic cavity

Nikolai Khokhlov, GRIGORIY KNYAZEV, Boris Glavin, YAKOV SHTYKOV, Oleg Romanov, and Vladimir Belotelov

Doc ID: 301954 Received 07 Jul 2017; Accepted 11 Aug 2017; Posted 17 Aug 2017  View: PDF

Abstract: In this letter we introduce the approach for active plasmon polaritons manipulation via acoustic waves at sub-terahertz frequency range. Considered acoustic structures are designed as phononic Fabry-Pérot microresonators where mirrors are presented with acoustic superlattice and the structure surface, plasmonic grating is placed on top of the formed acoustic cavity. It provides phonon localization in the vicinity of the plasmonic grating at the frequencies within the phononic stop-band enhancing phonon-light interaction. We consider the phonon excitation with femtosecond laser pulse shining on the plasmonic grating. Appropriate theoretical model was used to describe the acoustic process causes by pump laser pulse in the GaAs/AlAs based acoustic cavity with gold grating on top. The highest modulation is achieved at excitation of propagating surface plasmon-polaritons and hybridization of propagating and localized plasmons. The calculations show the relative changes of optical reflectivity of the structure are more than one order of magnitude higher as for the structure without plasmonic film.

Two-color Walking Peregrine Solitary Waves

Fabio Baronio, Shihua Chen, and Dumitru Mihalache

Doc ID: 297824 Received 13 Jun 2017; Accepted 11 Aug 2017; Posted 15 Aug 2017  View: PDF

Abstract: We study extreme localization of light, evolving upon a non-zero background,in two color parametric wave interaction in nonlinear quadratic media. We report the existence of quadratic Peregrine solitary waves, in the presence of significant group velocity mismatch between the waves (or Poynting vector beam walk off), in the regime of cascading second-harmonic generation. This finding opens a novel path for the experimental demonstration of extreme rogue waves in ultrafast quadratic nonlinear optics.

Moiré deflectometry-based position detection for optical tweezers

Ali Akbar Khorshad, Nader Reihani, and Mohammad Tavassoli

Doc ID: 298239 Received 22 Jun 2017; Accepted 11 Aug 2017; Posted 14 Aug 2017  View: PDF

Abstract: Optical Tweezers are proven indispensable tools for pico-Newton range force spectroscopy. A quadrant pho- todiode positioned at the back focal plane of optical tweezers’ condenser is commonly used for locating the trapped object inside the trap. In this letter, for the first time to the best of our knowledge, we introduce a moiré pattern-based detection method for optical tweezers. We show, both theoretically and experimentally, that this detection method could provide considerably bet- ter position sensitivity compared to the commonly used detection systems. For instance, position sensitivity for a trapped 2.17μm polystyrene bead is shown to be 71% better than the commonly used quadrant photodiode- based detection method. Our theoretical and experi- mentalresultsareingoofagreement.

Optimization of primary Kerr optical frequency combsfor tunable microwave generation

Yanne Chembo and Souleymane Diallo

Doc ID: 298036 Received 13 Jun 2017; Accepted 10 Aug 2017; Posted 14 Aug 2017  View: PDF

Abstract: We analyze the condition under which Kerr combs generate the highest microwave output power after photodetection. These optimal comb states correspond to configurations the sidemode-to-pump ratio is the highest possible. For the case of primary combs, we show how the interplay between power and frequency of the pump laser critically influences this ratio, which has a direct influence on the phase noise performance of the generated microwaves. We also experimentally demonstrate primary combs with a sidemode-to-pump ratio as high as $-2$~dB, thereby leading to efficient energy conversion from the lightwave to the microwave frequency range.

1.4-7.2 μm broadband supercontinuum generation in an As-S chalcogenide tapered fiber pumped in the normal dispersion regime

Yingying Wang, Shixun Dai, Guangtao Li, Dong Xu, Chen You, Xin Han, Peiqing Zhang, Xunsi Wang, and XU PEIPENG

Doc ID: 301447 Received 04 Jul 2017; Accepted 10 Aug 2017; Posted 14 Aug 2017  View: PDF

Abstract: We report a broadband supercontinuum (SC) generation in chalcogenide (ChG) step-index tapered fibers pumped in the normal dispersion regime. The fibers consisting of As2S3 core and As38S62 cladding glasses were fabricated using the isolated stacked extrusion method. A homemade tapering platform allows us to accurately control the core diameters and transition region lengths of the tapered fibers. An SC generation spanning from 1.4 to 7.2 μm was achieved by pumping a 12-cm-long tapered fiber with femtosecond laser pulses at 3.25 μm. To the best of our knowledge, this is the broadest SC generation obtained experimentally in tapered fibers when pumped in the normal dispersion regime so far. The effects of waist diameter and transition region length of the tapered fiber on the SC spectral behavior were also investigated.

Few-layered ReS2 as saturable absorber for 2.8 μm solid state laser

Xian-cui Su, hongkun nie, Yiran Wang, Guoru Li, Bingzheng Yan, Baitao Zhang, Kejian Yang, and Jingliang He

Doc ID: 304038 Received 03 Aug 2017; Accepted 10 Aug 2017; Posted 16 Aug 2017  View: PDF

Abstract: A novel two-dimensional (2D) material member in TMD family, few-layered rhenium disulfide (ReS2) was prepared by liquid phase method successfully. By using open-aperture Z-scan method, the saturable absorption properties at 2.8 μm were characterized with a saturable fluence of 22.6 μJ/cm2 and a modulation depth of 9.7%. A passively Q-switched solid state laser at 2.8 μm was demonstrated by using the as-prepared ReS2 saturable absorber (SA) successfully. Under an absorbed pump power of 920 mW, a maximum output power of 104 mW was obtained with a pulse width of 324 ns and a repetition rate of 126 kHz. To the best of our knowledge, this is the first demonstration of applying ReS2 in an all-solid-state laser. Moreover, this represents the shortest pulses in Q-switched MIR lasers based on a 2D material as the saturable absorber, which demonstrated the superiority of ReS2 acting as optical modulator for generating short pulsed lasers. The results well prove that 2D ReS2 is a reliable optical modulator for MIR solid state lasers.

Measurements of Pancharatnam-Berry phase in modetransformations on hybrid-order Poincaré sphere

Yuanyuan Liu, Zhenxing Liu, Junxiao Zhou, Xiaohui Ling, Weixing Shu, Hailu Luo, and Shuangchun Wen

Doc ID: 300495 Received 22 Jun 2017; Accepted 08 Aug 2017; Posted 09 Aug 2017  View: PDF

Abstract: We report direct measurements of Pancharatnam-Berry phase in mode transformations on hybrid-orderPoincaré sphere. This geometric phase arises when the vector vortex states undergo a cyclic transforma-tion over a closed circuit on hybrid-order Poincaré sphere. The measured Pancharatnam-Berry phase isproportional to the solid angle of the closed circuit, as well as the variation of the total angular momentabetween north and south poles. More importantly, a zero Pancharatnam-Berry phase has been demon-strated, in spite of the vector vortex states taken through a closed circuit on the hybrid-order Poincarésphere. This interesting phenomenon can be explained as due to the zero Berry curvature.

Thermo-elastic optical coherence tomography

Tianshi Wang, Tom Pfeiffer, Min Wu, Wolfgang Wieser, GAETANO AMENTA, Wolfgang Draxinger, Ton van der Steen, Robert Huber, and Gijs van Soest

Doc ID: 302613 Received 19 Jul 2017; Accepted 08 Aug 2017; Posted 09 Aug 2017  View: PDF

Abstract: Absorption of nanosecond laser pulses induces rapid thermo-elastic deformation in tissue. A sub-micrometer scale displacement occurs within a few microseconds after the pulse arrival. In this Letter, we investigate the laser-induced thermo-elastic deformation using a 1.5 MHz phase-sensitive optical coherence tomography (OCT) system. A displacement image can be reconstructed, which enables a new modality of phase-sensitive OCT, called thermo-elastic OCT. Analysis of the results shows that the optical absorption is a dominating factor for the displacement. Thermo-elastic OCT is capable of visualizing inclusions that do not appear on the structural OCT image, providing additional tissue type information.

High-energy and efficient Raman soliton generation tunable from 1.98 to 2.29 µm in an all-silica-fiber thulium laser system

Jinzhang Wang, Shenghua Lin, Xiaoyan Liang, Mengmeng Wang, Peiguang Yan, Guohua Hu, Tom Albrow-Owen, Shuangchen Ruan, Zhipei Sun, and Tawfique Hasan

Doc ID: 296015 Received 15 May 2017; Accepted 08 Aug 2017; Posted 10 Aug 2017  View: PDF

Abstract: We demonstrate a compact, all-fiber-integrated laser system that delivers Raman solitons with a duration of ~100 fs and pulse energy of up to 13.3 nJ, continuously wavelength tunable from 1.98 to 2.29 µm via Raman-induced soliton self-frequency shift (SSFS) in a thulium-doped fiber amplifier. We realize a >90% efficiency of Raman conversion, the highest reported value from SSFS-based sources. This enables us to achieve >10 nJ soliton energy from 2.16 to 2.29 µm range, the highest energy demonstrated above 2.22 µm from an SSFS-assisted all-fiber tunable single-soliton-pulse source. Our simple and compact all-fiber tunable laser could serve as an efficient ~2 µm femtosecond source for a wide range of mid-IR applications.

Compact surface plasmon holographic microscopy for near-field film mapping

Jiwei Zhang, Siqing Dai, Chaojie Ma, Jianglei Di, and Jianlin Zhao

Doc ID: 298056 Received 13 Jun 2017; Accepted 08 Aug 2017; Posted 10 Aug 2017  View: PDF

Abstract: We develop a compact objective-coupling surface plasmon holographic microscopy with common-path configuration by introducing a Wollaston prism. Through off-axis hologram recording and numerical reconstruction, the amplitude- and phase-contrast surface plasmon resonance (SPR) images can be obtained simultaneously. Based on the four-layer SPR model, the thin film thickness distribution in near field can be mapped unambiguously using a novel demodulation method without priori knowledge. The technique demonstrates nondestructive and full-field measurement capabilities with sub-nanometer resolution, and can be applied to characterize films without and with absorption. Furthermore, owing to the high temporal stability, the recommended system shows great potentials for dynamic measurement of near-field tiny refractive index or thickness variation in chemistry, biomedicine field, etc.

High-contrast 10-fs OPCPA-based Front-End for multi-PW laser chains

Dimitrios Papadopoulos, Lourdes Patricia Ramirez, Kevin Genevrier, Lucas Ranc, Nathalie Lebas, Alain Pellegrina, Catherine LeBlanc, Pascal MONOT, Luc Martin, Ji-ping Zou, francois mathieu, Patrick Audebert, Patrick Georges, and Frederic Druon

Doc ID: 301812 Received 06 Jul 2017; Accepted 07 Aug 2017; Posted 07 Aug 2017  View: PDF

Abstract: Applications using multi-PW lasers necessitate high temporal pulse quality with a tremendous contrast ratio. The first crucial prerequisite, to achieve multi-PW peak power, is the generation of ultra-short pulses with good spectral phase quality. Second, to avoid any deleterious pre-ionisation effect on targets, ns-contrast better than 1012 is also targeted. In the framework of the Apollon 10-PW French laser program, we present a high-contrast 10-fs Front-End design study to inject high energetic Ti:sapphire PW-lasers. The contrast ratio has been measured and analyzed in different time ranges highlighting the different major contributions for each scale.

2.3-μm Tm3+:YLF Mode-locked laser

Rémi Soulard, Aleksey Tyazhev, Jean-Louis DOUALAN, Alain BRAUD, Ammar Hideur, Mathieu Laroche, Bin Xu, and Patrice Camy

Doc ID: 302912 Received 21 Jul 2017; Accepted 07 Aug 2017; Posted 16 Aug 2017  View: PDF

Abstract: A passively mode-locked Tm:YLF laser emitting at 2.3µm is reported for the first time. The CW stable mode locking operation is obtained with a SESAM at a repetition rate of 100 MHz. The average output power is 165 mW for a pulse duration of 94 ps.

Transmission performance of 90°-bend optical waveguides fabricated in fused silica by femtosecond laser inscription

Jing Lv, Jing Bai, Kaiming Zhou, Xuesong Mei, Kedian Wang, Ming Li, and Cheng Guanghua

Doc ID: 301018 Received 30 Jun 2017; Accepted 07 Aug 2017; Posted 07 Aug 2017  View: PDF

Abstract: The L-shape waveguide was written in fused silica using femtosecond laser with beam shaping. The guiding structure supports good light turning, 0.88 dB/turn was achieved at the silica-air interface. By using finite-different time-domain (FDTD) method, the turn loss due to the turning structure and refractive index of the L-shape waveguide has been simulated. The results show that the proposed method has unprecedented flexibility in fabricating 90°-bend waveguide.

Dual-frequency Doppler lidar for wind detection with superconducting nanowire single-photon detector

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

Doc ID: 296302 Received 18 May 2017; Accepted 06 Aug 2017; Posted 07 Aug 2017  View: PDF

Abstract: A dual-frequency direct detection Doppler lidar is demonstrated using a superconducting nanowire single-photon detector (SNSPD) at 1.5 μm. The so-called double-edge technique is implemented by using a dual-frequency laser pulse rather than using a double-channel Fabry-Perot interferometer. Such a modification to the reported lidars enhances the frequency stability in the system level. Using the time-division multiplexing method, only one piece of SNSPD is used in the optical receiver, making the system simplified and robust. The SNSPD is adopted to enhance the temporal resolution since it offers merits of high quantum efficiency, low dark count noise, no after-pulsing probability, and high maximum count rate. Two telescopes that point westward and northward at a zenith angle of 30° are used to detect the line-of-sight wind components, which are used to synthesize the horizontal wind profile. Horizontal wind profiles up to the altitude of about 2.8 km are calculated with vertical spatial/temporal resolution of 10 m/10 s. Wind dynamic evolution and vertical wind shears are observed clearly.

Self-starting optical-electrical-optical homodyne clock-recovery for phase modulated signals

Ehsan Sooudi, Andrew Ellis, and Robert Manning

Doc ID: 302197 Received 17 Jul 2017; Accepted 06 Aug 2017; Posted 10 Aug 2017  View: PDF

Abstract: We propose a novel self-homodyne optical-electrical-optical clock recovery technique for binary phase-shift keying signals using commercial optical and electrical components. We present the principle of operation as well as a proof-of-concept experiment for a 10.7 Gb/s NRZ BPSK signal clock-recovery transmitted over a dispersion compensated link of 20 km of SMF. Suppression of pattern related frequency noise at the output of the recovered clock is shown. The timing jitter of the recovered clock at 10.7 GHz was measured to be ~450 fs (integration range: 100 Hz -10 MHz).

Femtosecond laser inscription of Bragg grating waveguides in bulk diamond

Vibhav Bharadwaj, arnaud courvoisier, Toney Fernandez, Roberta Ramponi, Gianluca Galzerano, Joshua Nunn, Martin Booth, Roberto Osellame, Shane Eaton, and Patrick Salter

Doc ID: 297023 Received 29 May 2017; Accepted 05 Aug 2017; Posted 07 Aug 2017  View: PDF

Abstract: Femtosecond laser writing is applied to form Bragg grating waveguides in the diamond bulk. Type II waveguides are integrated with a single pulse point-by-point periodic laser modification positioned towards the edge of the waveguide core. These photonic devices, operating in the telecommunications band, allow for simultaneous optical waveguiding and narrowband reflection from a 4th order grating. This fabrication technology opens the way towards advanced 3D photonic networks in diamond for a range of applications.

Chirped fiber tip Fabry-Perot interferometer

Xinpu Zhang, Liyang Shao, Xihua Zou, Bin Luo, Wei Pan, and Lianshan Yan

Doc ID: 301228 Received 26 Jul 2017; Accepted 05 Aug 2017; Posted 07 Aug 2017  View: PDF

Abstract: We demonstrate a novel fiber tip Fabry-Perot (FP) interferometer with chirped spectral characteristic. The FP interferometer is formed by an etched chirped fiber Bragg grating (FBG) and the fiber tip broadband end-face mirror, and the etched chirped FBG are prepared by a dynamic chemical etching process, shaping the taper and reducing the size from 125μm to just a few micrometers. Due to the spectral characteristic of the etched chirped FBG, the different resonance wavelengths are corresponding to different gating positions which given rise to the gradient cavity length in the chirped fiber tip FP interferometer, thus, this FP interferometer possesses a chirped interference spectra. Subsequently, the FP interferometer is fabricated and temperature response is investigated by measuring the wavelength shift of the resonance dips in the reflection spectrum. Significantly, because of its especial interference principle and configuration, we experimentally demonstrate this FP interferometer can be used for the spatial localization of the external temperature perturbations. As a robust and ultra-compact fiber sensor, which has location capability, this fiber interferometer has a wide potential application in monitoring the gradient or spatial distribution of the external fields.

Low-concentrated solar-pumped laser via transverse-excitation fiber-laser geometry

Taizo Masuda, Mitsuhiro Iyoda, Yuta Yasumatsu, and Masamori Endo

Doc ID: 298156 Received 19 Jun 2017; Accepted 04 Aug 2017; Posted 07 Aug 2017  View: PDF

Abstract: We demonstrate an extremely low-concentrated solar-pumped laser (SPL) using a fiber laser with transverse excitation geometry. A low concentration factor is highly desired in SPLs to eliminate the need for precise solar tracking and to considerably increase the practical applications of SPL technology. In this paper, we have exploited the intrinsic low-loss property of silica fibers to compensate for the extremely low gain coefficient of the weakly pumped active medium. A 40-m-long Nd3+-doped fiber coil is packed in a ring-shaped chamber filled with a sensitizer solution. We demonstrated a lasing threshold that is 15 times the concentration of natural sunlight and two orders of magnitude smaller than those of conventional SPLs.

Acoustic Detection of Resonance-Enhanced Multiphoton Ionization for Spatially-Resolved Temperature Measurement

YUE WU, Mark GRAGSTON, and zhili zhang

Doc ID: 301412 Received 03 Jul 2017; Accepted 04 Aug 2017; Posted 04 Aug 2017  View: PDF

Abstract: In this work, acoustic detection of resonance-enhanced multiphoton ionization (A-REMPI) is characterized and used to measure spatially-resolved O2 rotational temperature in air. The acoustic signal is generated using O2 REMPI in air and is detected by a single microphone operating within the audible range. Compared to electron number measurements by coherent microwave scattering, nonlinear light absorption and subsequent local pressure perturbation are captured by the microphone. Typical acoustic cycle of compression and rarefication of the acoustic wave is observed in the A-REMPI. Since the pressure perturbation can be regarded as close to thermodynamic equilibrium, the rotational temperature measured by A-REMPI is lower and closer to the realistic condition.

Laser-based optoelectronic generation of narrow-band microwave chaos for radars and radio-communication scrambling

Yanne Chembo

Doc ID: 299367 Received 20 Jun 2017; Accepted 04 Aug 2017; Posted 04 Aug 2017  View: PDF

Abstract: We propose an optoelectronic oscillator architecture for narrow-band microwave chaos generation. In the time domain, the microwave signal features has a slowly-varying envelope with amplitude and phase chaos, while in the frequency domain, it is quasi-indistinguishable from a band-limited white noise. A full theoretical analysis is performed to investigate the stability properties and route to chaos for the microwave oscillations. We experimentally generate the narrow-band microwave chaos with a central frequency of $3$~GHz and a bandwidth of only $16$~MHz, and we discuss the applications for radar engineering and radio-communication scrambling applications.

Holmium thin-disk laser based on Ho:KY(WO4)2 / KY(WO4)2 epitaxy with 60% slope efficiency and simplified pump geometry

Xavier Mateos, Samir Lamrini, Karsten Scholle, Peter Fuhrberg, Sergei Vatnik, Pavel Loiko, Ivan Vedin, Magdalena Aguilo, Francesc Diaz, Uwe Griebner, and Valentin Petrov

Doc ID: 302516 Received 17 Jul 2017; Accepted 04 Aug 2017; Posted 10 Aug 2017  View: PDF

Abstract: We report on the first Holmium (Ho3+) monoclinic double tungstate thin-disk laser. It is based on a 250 µm-thick 3 at. % Ho:KY(WO4)2 active layer grown on a (010)-oriented KY(WO4)2 substrate. When pumped by a Tm-fiber laser at 1960 nm with a single-bounce (single double-pass) pump geometry, the continuous-wave Ho:KY(WO4)2 thin-disk laser generated 1.01 W at 2057 nm corresponding to a slope efficiency η of 60% and a laser threshold of only 0.15 W. Implementing a double-bounce (second double-pass) for the pump, the output of this laser was scaled to 1.57 W with η = 55%. The maximum stimulated-emission cross-section σSE of the Ho3+ ions in the epitaxial layer reaches 2.5×10-20 cm2 at 2056.5 nm for E || Nm. The Ho:KY(WO4)2 epitaxial structures are promising for multi-watt mode-locked thin-disk lasers at ~2.06 µm.

Loss reduction of silicon-on-insulator waveguides for deep mid-infrared applications

Liuqing He, Yuhao Guo, Zhaohong Han, Kazumi Wada, Lionel Kimerling, Jurgen Michel, Anuradha Agarwal, Guifang li, and Lin Zhang

Doc ID: 298207 Received 19 Jun 2017; Accepted 04 Aug 2017; Posted 10 Aug 2017  View: PDF

Abstract: We show that propagation loss of optical waveguides based on silicon-on-insulator (SOI) material platform can be greatly reduced. The loss, including SiO2 absorption and substrate leakage but no scattering loss, is found to be 0.024 and 0.53 dB/cm in the deep mid-infrared at 4.8 and 7.1 μm wavelengths, where the material absorption in SiO2 is 100 and 1000 dB/cm, respectively. The obtained loss becomes negligible, compared to scattering loss in Si waveguides. This is enabled by using the TE10 mode in a pedestal waveguide. We also show that the TE10 mode can be excited in the proposed waveguide by the fundamental mode with a coupling efficiency of >94%. Low propagation loss, high coupling efficiency, and fabrication-friendly design would make it promising for practical use of SOI devices in the deep mid-infrared.

Ultra-wideband Ge-rich silicon germanium integrated Mach Zehnder interferometer for mid infrared spectroscopy

Vladyslav Vakarin, Joan Manel Ramirez, Jacopo Frigerio, Andrea Ballabio, Xavier LE ROUX, Qiankun Liu, David Bouville, Laurent Vivien, Giovanni Isella, and Delphine Marris-Morini

Doc ID: 301643 Received 03 Jul 2017; Accepted 03 Aug 2017; Posted 14 Aug 2017  View: PDF

Abstract: This work explores the use of Ge-rich Si0.2Ge0.8 waveguides on graded Si1-xGex substrate for the demonstration of ultra-wideband photonic integrated circuits in the mid infrared (mid-IR) wavelength range. We designed, fabricated and characterized broadband Mach Zehnder interferometers (MZI) fully covering a range of 3µm in the mid-IR band. The fabricated devices are operating indistinctly in quasi-TE and quasi-TM polarizations and have an extinction ratio (ER) higher than 10 dB over the entire operating wavelength range. The obtained results are in good correlation with theoretical predictions, while numerical simulations indicate that the device bandwidth can reach one octave with low additional losses. This work paves the way for further realization of mid-IR integrated spectrometers using low-index-contrast Si1-xGex waveguides with high Germanium concentration.

Integrated optical phased arrays for quasi-Bessel-beam generation

Jelena Notaros, Christopher Poulton, Matthew Byrd, Manan Raval, and Michael Watts

Doc ID: 301396 Received 03 Jul 2017; Accepted 03 Aug 2017; Posted 14 Aug 2017  View: PDF

Abstract: Integrated optical phased arrays for generating quasi-Bessel beams are proposed and experimentally demonstrated in a CMOS-compatible platform. Due to their elongated central beams, Bessel beams have applications in a range of fields, including multi-particle trapping and laser lithography. In this Letter, continuous Bessel theory is manipulated to formulate the phase and amplitude conditions necessary for generating free-space-propagating Bessel-Gauss beams using on-chip optical phased arrays. Discussion of the effects of select phased array parameters on the generated beam's figures of merit is included. A one-dimensional splitter-tree-based phased array architecture is modified to enable arbitrary passive control of the array's element phase and amplitude distributions. This architecture is used to experimentally demonstrate on-chip quasi-Bessel-beam generation with a ~14mm Bessel length and ~30μm power full-width half-maximum.

Intermodal modulational instability in graded-index multimode optical fibers

Richard Dupiol, Abdelkrim Bendahmane, Katarzyna Krupa, Julien Fatome, Alessandro Tonello, Marc FABERT, Vincent COUDERC, Stefan Wabnitz, and Guy Millot

Doc ID: 303090 Received 24 Jul 2017; Accepted 03 Aug 2017; Posted 03 Aug 2017  View: PDF

Abstract: We report on the experimental observation of an intermodal noise-seeded modulational instability process (MI) taking place in the normal dispersion regime of a few-mode graded-index optical fiber. Strong power dependence of the MI spectra is observed, with a peak gain modulation frequency that scales as the square root of the injected light power. These observations are in excellent agreement with the predictions of a bimodal-MI model.

High efficiency wide band SiNx-on-SOI grating coupler with low fabrication complexity

Pengfei Xu, Yanfeng Zhang, Zengkai Shao, Lin Liu, Lidan Zhou, Chunchuan Yang, Yujie Chen, and Siyuan Yu

Doc ID: 297536 Received 06 Jun 2017; Accepted 03 Aug 2017; Posted 04 Aug 2017  View: PDF

Abstract: Vertical chip-fiber grating coupler is a fundamental building block in integrated photonics, providing convenient on-wafer testing and packaging. Couplers based on silicon nitride (SiNx) material platform can achieve wider bandwidth than silicon-based couplers, but suffers from lower efficiency due to the relative low material refractive index. The efficiency of SiNx grating coupler can be improved by using high reflectivity silicon grating reflectors underneath. However, such silicon grating reflector requires several fabrication steps, including lithography, etching, high precision alignment (HPA), and chemical mechanical polishing (CMP). In this work, we demonstrate an easy-to-fabricate SiNx-on-SOI grating coupler only requiring a single patterning step without the need of HPA and CMP. A coupling coefficient of -2.5 dB and 1-dB-bandwidth of 65 nm have been experimentally measured.

Facile fabrication of flexible graphene FETs by sunlight reduction of graphene oxide

Jia-Nan Ma, YAN HE, Yan Liu, Dong-Dong Han, Yu-Qing Liu, Jiang-Wei Mao, Hao-Bo Jiang, and Yonglai Zhang

Doc ID: 297901 Received 14 Jun 2017; Accepted 03 Aug 2017; Posted 04 Aug 2017  View: PDF

Abstract: We reported here a facile fabrication of flexible graphene-based field effect transistors (FETs) by sunlight reduction of graphene oxide (GO) as channel material. As a mask-free and chemical-free method, sunlight photoreduction of GO without the use of any complex equipments, is simple and green. The resultant FET demonstrated excellent electrical properties (e.g., an optimized Ion/Ioff ratio of 111, hole mobility of 0.17 cm²/V×s), revealing great potential for development of flexible microelectrics. Additionally, since the RGO channel could be fabricated by sunlight treatment between two pre-patterned electrodes, the process features post-fabrication capability, which makes it possible to integrate graphene-based devices with given device structures.

More than 400 W random fiber laser with excellent beam quality

hanwei zhang, Long Huang, Pu Zhou, Xiaolin Wang, Xu Jiangming, and Xiaojun Xu

Doc ID: 297885 Received 12 Jun 2017; Accepted 03 Aug 2017; Posted 03 Aug 2017  View: PDF

Abstract: We report on the demonstration of a high power, high beam quality random fiber laser. It is a half-open cavity based on 130-meter-long large mode area step-index fiber with core diameter of 20 μm and numerical aperture of 0.08. The random laser cavity, whose central wavelength is 1120 nm, is pumped by an 1070 nm Yb-doped fiber oscillator. The maximum output power is 418 W with respect to the injected pump power of 588 W, corresponding to the optical-to-optical efficiency of 71%. The output power, spectral, and temporal characters are carefully presented and discussed, showing that such cavity can export high power random laser stably and effectively. The far field beam quality is also measured and the profile is nearly a Gaussian shape. This work provides an impactful method to advance the output power of random fiber lasers.

Designer surface plasmon dispersion on a one-dimensional periodic slot metasurface with glide symmetry

Miguel Camacho, Rhiannon Mitchell-Thomas, Alastair Hibbins, J. Sambles, and Oscar Quevedo-Teruel

Doc ID: 301299 Received 03 Jul 2017; Accepted 03 Aug 2017; Posted 03 Aug 2017  View: PDF

Abstract: In this letter we explore the dispersion of spoof surface plasmons supported by a single-layer glide-symmetric structure. This structure consists of an infinitely-long double-notched slot perforated in a metal layer. The presence of a degeneracy of the two lowest order modes at the Brillouin zone boundary, which have non-zero group velocity is explained and experimentally demonstrated. Further the dependence of the band-structure when glide-symmetric configuration is broken is also explored.

Electron-beam Excited Photon Emission from Monopole Mode of Plasmonic Nano-disc

xianglong miao, Kai Guo, Cheng Qian, J. Wang, Degang Zhao, and Kin Hung Fung

Doc ID: 301865 Received 06 Jul 2017; Accepted 03 Aug 2017; Posted 04 Aug 2017  View: PDF

Abstract: Plasmonic dark modes are not easy to be observed in the far field due to its weak photon emission. In contrast, it has been shown that dark mode can be excited effectively by a near field source such as electron beam. In this Letter, we show that the photon emission from the monopole-like dark mode supported on a plasmonic nano-disc could be unexpectedly strong when excited by an electron beam through its hole. Even though this monopole mode is considered to be dark, it is found that the emission can be even “brighter” than the dipolar bright modes when the electron beam energy is higher than 0.6c. Due high conversion efficiency from electron energy to photon energy, the results could also suggest an optical method for detection of high energy electrons passing through the hole.

Why you should not use the electric field to quantize in nonlinear optics

Nicolas Quesada and John Sipe

Doc ID: 301793 Received 10 Jul 2017; Accepted 02 Aug 2017; Posted 02 Aug 2017  View: PDF

Abstract: We show that using the electric field as a quantization variable in nonlinear optics leads to incorrect expressions for the squeezing parameters in SPDC and conversion rates in frequency conversion. This observation is related to the fact that if the electric field is written as a linear combination of bosonic creation and annihilation operators one cannot satisfy Maxwell's equations in a nonlinear dielectric.

Efficacy improvement in polymer LEDs via silver-nanoparticle doping in emissive layer

Sy-Hann Chen, Cheng-Liang Huang, Chang-Feng Yu, Guan-Fu Wu, Ya-Chu Kuan, Bo Han Cheng, and Yi Ru Li

Doc ID: 300907 Received 28 Jun 2017; Accepted 02 Aug 2017; Posted 04 Aug 2017  View: PDF

Abstract: The coupling of surface plasmons and excitons in the emissive layer (EML) can improve the performance of polymer light-emitting diodes (PLEDs). Silver nanoparticles (Ag-NPs) with a decahedron structure are prepared by the chemical reduction and photochemical methods and doped directly into the EML after the phase-transfer process. The surface plasmon resonance effect of Ag-NPs, which makes full use of quenched excitons and increases the efficiency of excitons in the EML in a PLED, enhances the current efficacy by a factor of 75 relative to that of the undoped reference device (from 0.22 to 16.64 cd/A). These results demonstrate that Ag-NPs can assist in simple and low-cost fabrication of high-performance polymer optoelectronic devices.

Phase matched nonlinear optics via patterning layered materials

Taylor Fryett, Alan Zhan, and Arka Majumdar

Doc ID: 297697 Received 09 Jun 2017; Accepted 02 Aug 2017; Posted 09 Aug 2017  View: PDF

Abstract: The ease of integration coupled with large second-order nonlinear coefficient of atomically thin layered 2D materials presents a unique opportunity to realize second-order nonlinearity in silicon compatible integrated photonic system. However, the phase matching requirement for second-order nonlinear optical processes makes the nanophotonic design difficult. We show that by nano-patterning the 2D material, quasi-phase matching can be achieved. Such patterning based phase-matching could potentially compensate for inevitable fabrication errors and significantly simplify the design process of the nonlinear nano-photonic devices.

Observation of 7p²P₃/₂ -> 7d²D optical transitions in 209 and 210 francium isotopes

Steinn Agustsson, Giovanni Bianchi, Roberto Calabrese, Lorenzo Corradi, Antonio Dainelli, Alen Khanbekyan, Carmen Marinelli, Emilio Mariotti, Luca Marmugi, Giuseppe Mazzocca, Luigi Moi, Leonardo Ricci, Leonardo Stiaccini, and Luca Tomassetti

Doc ID: 301826 Received 06 Jul 2017; Accepted 01 Aug 2017; Posted 07 Aug 2017  View: PDF

Abstract: We report on the direct experimental observation of the 7p²P₃/₂ -> 7d²D optical transitions in 209 and 210 francium isotopes. By continuously monitoring the fluorescence emitted by the isotopes collected in a magneto-optical trap, the electric dipole transitions 7p²P₃/₂ -> 7d²D₅/₂ of ²⁰⁹Fr, not yet experimentally observed, and 7p²P₃/₂ -> 7d²D₅/₂, 7p²P₃/₂ -> 7d²D₃/₂ of ²¹⁰Fr were detected as sub-Doppler depletion dips of the cold atom population. This approach allowed unambiguous identification of the excited state hyperfine structures, even in absence of a large stable vapor. Our findings demonstrate the effectiveness and the flexibility of fluorescence monitoring of trap depletion upon laser excitation, and broaden the experimental knowledge of francium isotopes and their electronic and nuclear properties. These results will have a relevant impact in on-going researches for low-energy testing of fundamental symmetries with francium, from atomic parity non-conservation to the electron dipole moment.

Bending Effect Characterization of Individual Higher Order Modes in Few-Mode Fibers

Yao Xu, Guobin Ren, Youchao Jiang, Yixiao Gao, Haisu Li, Wenxing Jin, Yue Wu, ya shen, and Shuisheng Jian

Doc ID: 297337 Received 08 Jun 2017; Accepted 01 Aug 2017; Posted 01 Aug 2017  View: PDF

Abstract: We propose an approach to directly measure bending effect on individual modes in few-mode fibers using wavelength-scanning Spatially and Spectrally resolved imaging technique. By collecting fiber output beam profile with scanning wavelength at different bending diameters and analyzing peaks of its Fourier transformation, we have distinguished higher order modes of the fiber and investigated their bend loss, group delay, beam profile, mode rotation and mode splitting individually. We have experimentally verified with a multilayer core fiber at 1 cm - 8 cm bending diameters that its higher order modes experience more loss compared to lower order modes but delays at the same speed as bending diameter decreases. Mode splitting of LP₁₁ mode at small bending diameter due to bending-induced birefringence is also observed and discussed. This method provides an efficient tool to study bending effect on individual higher order modes in fibers and could be extended to study fiber stretching and twisting.

Multicore fiber Bragg grating based directional curvature sensor interrogated by broadband source with sinusoidal spectrum

Di Zheng, Javier Madrigal, Hailan Chen, David Barrera, and Salvador Sales

Doc ID: 297170 Received 01 Jun 2017; Accepted 01 Aug 2017; Posted 02 Aug 2017  View: PDF

Abstract: A simple, spectral-drift-insensitive interrogation scheme for multicore fiber Bragg grating based directional curvature sensor is proposed. The basic principle is to transform the wavelength shift of FBGs into the reflected power variation, which is accomplished by utilizing broadband source with sinusoidal spectrum. The closed-form expression of the relationship between the reflected power of FBG and the corresponding peak wavelength is derived for the first time to our knowledge, therefore the peak wavelength of FBG can be precisely interrogated by using single photodiode. The experimental results show that, with respect to conventional wavelength measurement by optical spectrum analyzer, the demodulated wavelength error by our proposed interrogation scheme is within ±20pm. The proposed scheme is further extended to interrogate the direction and curvature using multicore fiber Bragg grating based curvature sensor, the interrogated curvature with error less than 8% is achieved.

Thickness-dependent nonlinear optical properties of CsPbBr3 perovskite nanosheets

Juna Zhang, Tian Jiang, Xin Zheng, chao shen, and Xiang'ai Cheng

Doc ID: 302661 Received 17 Jul 2017; Accepted 31 Jul 2017; Posted 01 Aug 2017  View: PDF

Abstract: Halide perovskite have attracted significant attentions because of excellent optical properties. Here, we study the optical properties of CsPbBr3 perovskite nanosheets and observe that the nonlinear optical properties can be tuned by thickness. The photoluminescence (PL) properties and nonlinear absorption effects induced by saturation absorption (SA) and two-photon absorption (TPA) in CsPbBr3 nanosheets with different thicknesses (from 104.6 nm to 195.4 nm) have been studied. The PL intensity increases nearly 3 times with changing from the thinnest one to the thinnest under the same excitation condition. Specifically, this phenomenon is almost same no matter SA or TPA effect happens when changed the excitation wavelength. The PL lifetime ( τ ) varies inversely with thickness. When SA happens, τ decreases from 11.54 ns to 9.43 ns. While when TPA happens, new decay channels emerges with the increase of thickness. Besides, both saturation intensity (I_sat) and modulation depth are proportional to thickness (I_sat rises from 3.12 GW/cm2 to 4.79 GW/cm2, modulation depth increases from 18.6% to 32.3%) while the TPA coefficient ( β) is inversely proportional with the thickness (decreases from 10.94 cm/GW to 4.73 cm/GW). In addition, quantum yields (QYs) and thickness are in the direct ratio. This work advocates great promise for nonlinear optical properties related photonics devices.

A 2D-3D switchable display based on passive polymeric lenticular lens array and electrically suppressed ferroelectric liquid crystal

L Shi, abhishek srivastava, Alwin Tam, Vladimir Chigrinov, and Hoi-Sing Kwok

Doc ID: 301030 Received 30 Jun 2017; Accepted 31 Jul 2017; Posted 04 Aug 2017  View: PDF

Abstract: In this article, we demonstrate a compact fast 2D-3D switchable lens unit based on a polarization-sensitive micro-lens array and an electrically suppressed helix ferroelectric liquid crystal (ESHFLC) cell that works as a polarization selector unit. The ESHFLCs offer high extinction ratio (~10k:1), between the two perpendicular polarization azimuth of the impinging light, at a low applied electric field (~1.7 V/m) with a short response time (< 50s). A special driving scheme, to switch 2D and 3D, has been developed to avoid the unwanted DC balancing artifacts of the ESHFLC. The proposed lens unit is characterized by low power consumption, ultrafast response and 3D crosstalk < 5%, and therefore, can find application in TVs, cell phones etc.

Distribution of continuous variable quantum entanglement at a telecommunication wavelength over 20 km of optical fiber

JinXia Feng, Zhenju Wan, Yuanji Li, and Kuanshou Zhang

Doc ID: 298065 Received 13 Jun 2017; Accepted 31 Jul 2017; Posted 03 Aug 2017  View: PDF

Abstract: Distribution of continuous variable (CV) Einstein-Podolsky-Rosen (EPR)-entangled beams at a telecommunication wavelength of 1550 nm over single mode fibers are investigated. EPR-entangled beams with quantum entanglement of 8.3 dB is generated using a single nondegenerate optical parametric amplifier based on a type-II periodically poled KTiOPO4 crystal. When one beam of the generated EPR-entangled beams is distributed over 20 km of single mode fiber, 1.02 dB quantum entanglement can still be measured. The degradation of CV quantum entanglement in a noisy fiber channel is theoretically analyzed considering the effect of depolarized guided acoustic wave Brillouin scattering in optical fibers. The theoretical prediction is in good agreement with the experimental results.

Visible Laser Emission from a Praseodymium Doped Fluorozirconate Guided-Wave Chip

Champak Khurmi, Sam Thoday, Tanya Monro, George Chen, and David Lancaster

Doc ID: 300563 Received 21 Jun 2017; Accepted 30 Jul 2017; Posted 31 Jul 2017  View: PDF

Abstract: We report visible continuous wave laser emission at 636 nm from a praseodymium doped fluorozirconate glass guided-wave chip laser. This ultra-fast laser inscribed gain chip is demonstrated to be a compact and integrated laser module. The laser module, pumped by 442 nm GaN laser diodes, generates >8 mW lasing output with a beam quality of M² ~ 1.15 × 1.1 (±0.1). To the best of our knowledge, this is the first visible laser emission from a glass based waveguide chip laser.

Highly sensitive temperature sensor based on ultra-compact Mach-Zehnder interferometer with side-opened channels

Ming Deng, Leiguang Liu, Yong Zhao, Guolu Yin, and Tao Zhu

Doc ID: 295760 Received 12 May 2017; Accepted 29 Jul 2017; Posted 07 Aug 2017  View: PDF

Abstract: We demonstrated an ultra-compact and highly sensitive temperature sensor by use of an in-fiber Mach–Zehnder interferometer (MZI) with side-opened channels. The MZI was constructed by off-center splicing a thin piece of microstructured optical fiber (MOF) between two single-mode fibers (SMFs). Then, two side-opened channels were drilled through the MOF along the transverse direction by using a femtosecond laser to let the liquid with high thermo-optic coefficient enter into the air cavity of the MZI. Due to the large effective refractive index difference between the core mode and the cavity mode excited by the offset splicing point, the scale of the MOF-based MZI can be reduced to several hundred micrometers, which is the most compact structure among the in-line optical fiber MZIs, to the best of our knowledge. Experimental results show that the MOF-based MZI infiltrated with isopropanol has a temperature sensitivity up to 3.6nm/°C with small strain cross sensitivity of 0.0001°C /με in the temperature range of 18-48°C, which makes it a competitive fiber sensor in highly sensitive temperature sensing applications including healthcare, consumer electronics, and so on.

Rapid focus map surveying for whole slide imaging with continues sample motion

Jun Liao, Yutong Jiang, Zichao Bian, Bahareh Mahrou, Aparna Nambiar, Alexander Magsam, Kaikai Guo, S Wang, Yongku Cho, and Guoan Zheng

Doc ID: 301564 Received 05 Jul 2017; Accepted 28 Jul 2017; Posted 03 Aug 2017  View: PDF

Abstract: Whole slide imaging (WSI) has recently been cleared for primary diagnosis in the US. A critical challenge of WSI is to perform accurate focusing in high speed. Traditional systems create a focus map prior to scanning. For each focus point on the map, sample needs to be static in the x-y plane and axial scanning is needed to maximize the contrast. Here we report a novel focus map surveying method for WSI. The reported method requires no axial scanning, no additional camera and lens, works for stained and transparent samples, and allows continuous sample motion in the surveying process. It can be used for both brightfield and fluorescence WSI. By using a 20X, 0.75 NA objective lens, we demonstrate a mean focusing error of ~0.08 microns in the static mode and ~0.17 microns in the continuous motion mode. The reported method may provide a turnkey solution for most existing WSI systems for its simplicity, robustness, accuracy, and high-speed. It may also standardize the imaging performance of WSI systems for digital pathology and find other applications in high-content microscopy such as DNA sequencing and time-lapse live-cell imaging.

Real-time measurement of temperature distribution inside gain medium of a diode-pumped Er3+/Yb3+ 1.55-µm laser

Chenchen Xu, Yidong Huang, Yanfu Lin, Jian Huang, Xinghong Gong, Zundu Luo, and Chen Yujin

Doc ID: 302215 Received 12 Jul 2017; Accepted 28 Jul 2017; Posted 03 Aug 2017  View: PDF

Abstract: A scheme to measure temperature distribution inside a gain medium of a diode-pumped solid-state laser is proposed based on fluorescence intensity ratio technique. By recording the temperature-dependent upconversion fluorescence related to the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions of Er3+, real-time temperature distribution inside an Er3+:Yb3+:LuAl3(BO3)4 crystal end-pumped by a 976-nm diode laser can be measured while a 1.55-µm laser is operating. Influences of pump power, output power and output mirror transmissivity on temperature distribution inside the gain medium are investigated. This scheme can conveniently and accurately measure the temperature distribution along laser path in a rare earth doped gain medium in real time.

High-performance MoS₂/Si heterojunctions broadband photodetectors from deep UV to NIR

Zhenhua Lou, Longhui Zeng, Yuange Wang, Di Wu, Tingting Xu, Zhifeng Shi, Yongtao Tian, Xin Jian Li, and Yuen Tsang

Doc ID: 301347 Received 04 Jul 2017; Accepted 28 Jul 2017; Posted 31 Jul 2017  View: PDF

Abstract: Polycrystalline 2D Layered molybdenum disulfide (MoS₂) films were synthesized via a thermal decomposition method. The MoS₂/Si heterostructrues were constructed in situ by synthesis MoS₂ on plane Si substrates. Such MoS₂/Si heterostructrues exhibited high sensitivity to light illumination with wavelengths ranged from the deep ultraviolet to the near-infrared. Photoresponse analysis reveals that a high responsivity of .1 A/W, a specific detectivity of 1.63×10¹² Jones and a fast response speed of 21.6/65.5 μs were achieved. Notably, the MoS₂/Si heterojunction photodetecor could operate with excellent stability and repeatability over a wide frequency range up to 150 kHz. The high performance could be attributed to the high-quality heterojunction between MoS₂ and Si obtained by in situ fabrication process. Such high performance suggests that MoS₂/Si heterostructures could have great potential for optoelectronic applications.

Parametric Control of Thermal Self-Pulsation in Microcavities

Luigi Di Lauro, jin li, David Moss, Roberto Morandotti, Sai Tak Chu, Marco Peccianti, and Alessia Pasquazi

Doc ID: 300508 Received 22 Jun 2017; Accepted 28 Jul 2017; Posted 02 Aug 2017  View: PDF

Abstract: We propose a scheme for bifurcation and self-pulsing control in micro-cavities based on the interplay between a slow nonlinearity, such as thermo-optical, free carriers-induced or opto-mechanical, and the ultrafast Kerr effect. We show here that Hopf bifurcations can be efficiently controlled with a low energy control signal via four wave mixing. Our results show that new strategies are possible for designing efficient micro-cavity based oscillators and sensors. Moreover, they provide new understanding on the effect of coherent wave mixing in the thermal stability regions of optical microcavities, fundamental for microcavity based applications in communications, sensing and metrology, including optical micro-combs.

Discretely Selectable Multi-Wavelength Operation of a SESAM Mode-Locked Nd:YVO4 Laser

Tanant Waritanant and Arkady Major

Doc ID: 300525 Received 20 Jun 2017; Accepted 28 Jul 2017; Posted 28 Jul 2017  View: PDF

Abstract: We report on a SESAM mode-locked Nd:YVO4 laser operating at discretely selectable 1064.0, 1073.0, 1085.1 nm wavelengths with the average output powers of more than 2.2 W at each of the three wavelengths. The optical-to-optical efficiencies and the slope efficiencies were larger than 19% and 29% for each of the three wavelengths and the pulse durations at the highest output powers were 13.1, 10.3, and 8.4 ps, respectively.

Ultrabroadband tunable OPA design using spectrally broadened pump source

Seyed Ali Rezvani, Zuofei Hong, xiaoxiao pang, Shun Wu, Qingbin Zhang, and Peixiang Lu

Doc ID: 301700 Received 05 Jul 2017; Accepted 27 Jul 2017; Posted 28 Jul 2017  View: PDF

Abstract: A robust optical parametric amplifier (OPA) scheme is proposed in which we have experimentally achieved broadband bandwidth for a collinear OPA design that exhibits good beam quality and spatial distribution using a type-I β barium borate (BBO) crystal. The applied pump pulses are simultaneously spectrally broadened and temporally stretched in a multi-plate system, before being used to amplify the temporally stretched white light. In this case, the phase matching can be obtained for a broad range of wavelengths and we have managed to achieve bandwidths three times broaderthan a conventional narrow band pumped collinear OPA. With a bandwidth as broad as 400 nm centered at 1400 nm as well as a broadband angular dispersion free idler, the signal bandwidth supports transform-limited(TL) pulses as short as 7.5 fs which is correspondent to sub-two optical cycles for this center wavelength. Furthermore, the system is easily tunable over a 400 nm range of bandwidths starting from 1100 nm to 1500 nm.The proposed scheme provides a versatile NIR/MIR source with broad bandwidth and fine tuning capability which paves the way for ultrafast spectroscopy and strong field applications.

Observation of fiber fuse propagation speed with high temporal resolution using heterodyne detection and time-frequency analysis

Shoulin Jiang, Lin Ma, Xinyu Fan, Wang Shuai, and Zuyuan He

Doc ID: 297616 Received 07 Jun 2017; Accepted 27 Jul 2017; Posted 31 Jul 2017  View: PDF

Abstract: We demonstrate real-time observation of fiber fuse propagation speed with high temporal resolution of 2.4 μs by combining heterodyne detection and time-frequency analysis. The periodic oscillation of fiber fuse propagation speed over a power range from 2.5 W to 6.3 W with an increase in oscillation frequency from 6.18 to 6.45 kHz was observed. The relaxation processes before reaching equilibrium have been studied during initiation and power modulation processes for the first time to the best of our knowledge. We confirm that the speed variation is largely dependent on the power fluctuation during termination process. The proposed method is useful for validating the different fiber fuse heat conduction models.

Variability of adjacency effects in sky reflectance measurements

Philipp Groetsch, Peter Gege, Stefan Simis, Marieke Eleveld, and Steef Peters

Doc ID: 302164 Received 13 Jul 2017; Accepted 27 Jul 2017; Posted 01 Aug 2017  View: PDF

Abstract: Sky reflectance Rsky(λ) is used to correct in situ reflectance measurements in the remote detection of water colour. We analysed the directional and spectral variability in Rsky(λ) due to adjacency effects against an atmospheric radiance model. The analysis is based on one year of semi-continuous Rsky(λ) observations that were recorded in two azimuth directions. Adjacency effects contributed to Rsky(λ) dependent on season and viewing angle, and predominantly in the near-infrared (NIR). For our test area, adjacency effects spectrally resembled a generic vegetation spectrum. The adjacency effect was weakly dependent on the magnitude of Rayleigh- and aerosol-scattered radiance. Reflectance differed between viewing directions 5.4 ± 6.3% for adjacency effects and 21.0 ± 19.8% for Rayleigh- and aerosol-scattered Rsky(λ), in the NIR. It is discussed under which conditions in situ water reflectance observations require dedicated correction for adjacency effects. We provide an open source implementation of our method to aid identification of such conditions.

Levitation and propulsion of a Mie-resonance particle by a surface plasmon

Alexey Maslov

Doc ID: 298026 Received 13 Jun 2017; Accepted 26 Jul 2017; Posted 27 Jul 2017  View: PDF

Abstract: It is predicted that the optical force induced by a surface plasmon can form a stable equilibrium position for a resonant particle at a finite distance from the surface. The levitated particle can be efficiently propelled along the surface without touching it. The levitation originates from the strong interaction of the particle with the surface.

Gas mixture for deep-UV plasma emission in hollow-core photonic crystal fiber

Foued Amrani, Frédéric Delahaye, Benoît Debord, Luís Lemos Alves, frederic gerome, and Fetah Benabid

Doc ID: 302121 Received 10 Jul 2017; Accepted 25 Jul 2017; Posted 26 Jul 2017  View: PDF

Abstract: We report on the first DUV/UV emission using a highly compact microwave-driven plasma-core photonic crystal fiber. The latter consists of a few cm long micro-plasma column of a gas mixture in the core of Kagome hollow-core photonic crystal fiber. The plasma is generated by non-intrusively exciting a ternary gas mixture of Argon, Nitrogen and Oxygen (Ar/N2/O2) with microwave resonator. Several spectral lines in the wavelength range of 200-450 nm were produced, guided by Ar-N2-O2 plasma-filled fiber, and controlled by simply varying the gas ratio of this gas mixture. An optimum gas mixture ratio was experimentally and theoretically identified for the strongest emission in the DUV range of 200-275 nm. The developed DUV emitting plasma-core fiber represents an important milestone towards the development of tunable and miniaturized DUV/UV laser sources.

Versatile hybrid plasmonic microfiber knot resonator

JIN-HONG LI, JIn-Hui Chen, Shaocheng Yan, YA-PING RUAN, Fei Xu, and Yanqing Lu

Doc ID: 295218 Received 05 May 2017; Accepted 25 Jul 2017; Posted 27 Jul 2017  View: PDF

Abstract: A planar, all-optical fiber polarizer-based device based on a hybrid plasmonic microfiber knot resonator (HPMKR) is demonstrated in this work. A microfiber knot resonator (MKR) can be flexibly attached to the gold film, which forms the hybrid plasmonic mode with high propagation loss. Therefore, the device can be used not only as a broadband polarizer, but also as a high quality resonator by tuning the geometry of the MKR. The polarizer has an extinction ratio of more than 15 dB ranging from 1200 to 1600 nm, and the Q-factor is more than 52,000 for one polarization state. For a chosen polarization, the resonator has an extinction ratio of nearly 15 dB, even though the diameter of the microfiber is more than 5 μm, which is unattainable for a normal MKR. By further optimizing and packaging, the device can be utilized as a weight sensor, with sensitivity of 18.28 pm/g (51.2 pm/kPa) for the cavity resonant wavelength. Further, a vibration sensor on HPMKR structure for detecting vibration from tens of hertz to several kilohertz is demonstrated.

L-shaped fiber-chip grating couplers with high-directionality and low-reflectivity fabricated with deep-UV lithography

Daniel Benedikovic, Carlos Alonso Ramos, Diego Pérez-Galacho, Sylvain GUERBER, Vladyslav Vakarin, Guillaume Marcaud, Xavier LE ROUX, Eric Cassan, Delphine Marris-Morini, Pavel Cheben, Frederic Boeuf, Charles BAUDOT, and Laurent Vivien

Doc ID: 301394 Received 04 Jul 2017; Accepted 21 Jul 2017; Posted 02 Aug 2017  View: PDF

Abstract: Grating couplers enable position-friendly interfacing of silicon chips by optical fibers. The conventional coupler designs call upon comparatively complex architectures to afford efficient light coupling to sub-micron silicon-on-insulator (SOI) waveguides. Conversely, the blazing effect in double-etched gratings provides high coupling efficiency, with reduced fabrication intricacy. In this work, we demonstrate for the first time the realization of an ultra-directional L-shaped grating coupler, seamlessly fabricated by using 193-nm deep-ultraviolet (deep-UV) lithography. We also show a single-step subwavelength waveguide-to-grating transition that provides an eight-fold reduction of the grating reflectivity, down to 1% (-20 dB). A measured coupling efficiency of -2.7 dB (54%) is achieved, with a bandwidth of 62 nm. These results open promising prospects for implementation of efficient, robust, and cost-effective coupling interfaces for sub-micrometric SOI waveguides, as desired for large-volume applications in silicon photonics.

Modelling of nonlinearity-compensated optical communication systems considering second-order signal-noise interactions

Nikita Shevchenko, Tianhua Xu, Domanic Lavery, Gabriele Liga, David Ives, Robert Killey, and Polina Bayvel

Doc ID: 296674 Received 24 May 2017; Accepted 20 Jul 2017; Posted 21 Jul 2017  View: PDF

Abstract: An analytical model considering modulation-dependent nonlinear effects and second-order interactions between signal and optical amplifier noise is presented for Nyquist-spaced wavelength-division-multiplexing optical communication systems. System performance of dual-polarisation (DP) modulation formats, such as DP-QPSK, DP-16QAM, and DP-64QAM is investigated using both the analytical model and numerical simulations. A good agreement between analytical and numerical results shows that, in the case of full-field nonlinearity compensation, accounting for second-order interactions becomes essential to predict system performance of both single-channel and multi-channel systems at optimum launched powers and beyond. This effect is validated via numerical simulations for signal bandwidths up to ~1 THz.

Instant and efficient second-harmonic generation and down-conversion in unprepared graded-index multimode fibers

Mohammad Amin Eftekhar, Zeinab Sanjabi Eznaveh, Jose Antonio-Lopez, Frank Wise, Demetrios Christodoulides, and Rodrigo Amezcua Correa

Doc ID: 295880 Received 25 May 2017; Accepted 19 Jul 2017; Posted 31 Jul 2017  View: PDF

Abstract: We show that germanium-doped graded-index multimode silica fibers can exhibit relatively high conversion efficiencies (~6.5%) for second-harmonic generation when excited at 1064 nm. This frequency-doubling behavior is also found to be accompanied by an effective down-conversion. As opposed to previous experiments carried out in single- and few-mode fibers where hours of preparation were required, in our system, these χ² related processes occur almost instantaneously. The efficiencies observed in our experiments are, to the best of our knowledge, among the highest ever reported in unprepared fibers.

Silicon nanobeam cavity for ultra-localized light-matterinteraction

Weiwei Zhang, samuel serna, Xavier LE ROUX, Laurent Vivien, and Eric Cassan

Doc ID: 292967 Received 26 Apr 2017; Accepted 19 Jul 2017; Posted 20 Jul 2017  View: PDF

Abstract: In this work, we theoretically and experimentally demonstrate an air mode silicon nanobeam cavity design unusually with dielectric mirrors. This designcombines an extremely strong localization of light matter interaction in the cavity center and a reduced sensitivity of the resonator wavelength to temperature or top cladding material refractive index variations. Theproposed approach allows an accurate control of the resonator cavity quality factor combined with a flexible choice of the cavity effective mode volume. Qfactors higher than 50,000 have been determined for such cavities and mode volumes smaller than (λ/n)^3 were achieved in the investigated configurations. Such a cavity design provides a robust approach to study thehybrid integration of various active materials in the silicon platform, including carbone nanotubes, III-V nanowires, graphene, etc, for light emission, modulation or detection

Ultra-short pulse fiber optical parametric oscillator

Thomas Gottschall, Jens Limpert, and Andreas Tünnermann

Doc ID: 297660 Received 08 Jun 2017; Accepted 12 Jul 2017; Posted 07 Aug 2017  View: PDF

Abstract: This work explores the frequency conversion and generation of short-pulses with an optical parametric oscillator based on micro-structured fibers. Depending on the operation regime, the optical cavity can either behave as a normal-dispersion cavity delivering linearly chirped pulses, which were externally compressed down to only 26 fs, or as a dispersion-managed oscillator, which directly delivered compressed pulses with a pulse duration of only 39 fs.

Long-wavelength-infrared solitons in air

Aleksandr Voronin and Aleksei Zheltikov

Doc ID: 296465 Received 22 May 2017; Accepted 17 Jun 2017; Posted 26 Jun 2017  View: PDF

Abstract: Dispersion and optical nonlinearity of atmospheric air in the long-wavelength infrared (LWIR) range are shown to enable unique soliton dynamics in freely propagating laser beams. Numerical analysis of three-dimensional spatiotemporal LWIR waveform evolution in air reveals soliton self-compression scenarios whereby ultrashort LWIR subterawatt pulses can be compressed to single-cycle terawatt field waveforms.

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