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https://read.qxmd.com/read/30768010/resonant-response-and-mode-conversion-of-the-microsphere-coupled-with-a-microfiber-coupler
#1
Ke Liu, Yang He, Ao Yang, Lei Shi, Lianglin Huang, Pu Zhou, Fufei Pang, Tingyun Wang, Xianglong Zeng
We experimentally investigate the resonant response in a microsphere coupled with a biconical microfiber coupler (MFC) composed of single- and/or few-mode fibers. The evolution between Lorentz and Fano resonances dependent on the phase difference of the supermodes is demonstrated along the coupling region of the MFC. A flexible narrow-linewidth add-drop filter can be simultaneously achieved with the advantage of easy alignment and efficiently evanescent coupling. In addition, the mode conversion process of the microsphere is demonstrated, and the purity of the LP11 mode in a coupler at the whispering gallery mode resonance is analyzed...
February 15, 2019: Optics Letters
https://read.qxmd.com/read/30696159/rayleigh-based-otdr-with-dynamic-modal-crosstalk-suppression
#2
Hiroshi Takahashi, Kunihiro Toge, Tomokazu Oda, Tetsuya Manabe
We propose and demonstrate a novel approach for measuring the modal attenuation of the splice loss of a purely LP11 mode group by using a Rayleigh-based OTDR with a dynamic modal crosstalk (XT) suppression technique for few-mode fibers (FMFs). With the proposed approach, the Brillouin loss interaction with a Brillouin Stokes beam co-propagating with the OTDR probe removes the modal XT caused at the modal conversion point and suppresses the accumulated modal XT that is detected. A preliminary experiment is demonstrated using spliced FMFs with a core-offset...
January 21, 2019: Optics Express
https://read.qxmd.com/read/30685706/optical-fiber-amplifier-for-quantitative-and-sensitive-point-of-care-testing-of-myoglobin-and-mirna-141
#3
Xiaofeng Liu, Hua Zhang, Shiya Qin, Qing Wang, Xiaohai Yang, Kemin Wang
A simple, sensitive, quantitative point-of-care testing (POCT) was developed integrating enzyme-linked DNA supersandwich amplification with optical fiber amplifier. The point-of-care (POC) assay can work in both "Turn-off" mode and "Turn-on" mode. Using myoglobin (Myo) and miRNA-141 as the model biomarker, as low as 0.5 nM Myo and 10 pM miRNA-141 could be detected. More importantly, the optical fiber amplifier, which was used as signal readout, exhibited low-cost, small size, rapid response, and easy operation...
January 18, 2019: Biosensors & Bioelectronics
https://read.qxmd.com/read/30645548/polarization-independent-orbital-angular-momentum-generator-based-on-a-chiral-fiber-grating
#4
Yan Zhang, Zhiyong Bai, Cailing Fu, Shen Liu, Jian Tang, Jian Yu, Changrui Liao, Ying Wang, Jun He, Yiping Wang
A polarization-independent orbital angular momentum (OAM) generator, based on a chiral fiber grating (CFG), is proposed and demonstrated for the first time, to the best of our knowledge. Helical phases were successfully excited in this device for the arbitrary polarization states of the input light, and the resulting OAM modes could be produced with a desired polarization state. The employed CFG was fabricated by twisting a fused few-mode fiber during hydrogen-oxygen flame heating. The polarization characteristics, helical phase, and purity of the coupled modes in the CFG were experimentally investigated for varying input light polarization states...
January 1, 2019: Optics Letters
https://read.qxmd.com/read/30645440/transverse-mode-switchable-fiber-laser-based-on-a-photonic-lantern
#5
Ning Wang, J C Alvarado Zacarias, J Enrique Antonio-Lopez, Z Sanjabi Eznaveh, Cedric Gonnet, Pierre Sillard, Sergio Leon-Saval, Axel Schülzgen, Guifang Li, Rodrigo Amezcua-Correa
We propose and experimentally demonstrate an intra-cavity transverse mode-switchable fiber laser based on a mode-selective photonic lantern and a few-mode Er-doped fiber amplifier. The six lowest-order LP modes can lase independently and are switchable by changing the input port of the photonic lantern. We measured the slope efficiency, mode intensity profile, and optical spectrum of each lasing mode. In addition, we demonstrate donut-shaped LP11 and LP21 modes using incoherent superposition and simultaneous lasing of the two degenerate modes...
December 10, 2018: Optics Express
https://read.qxmd.com/read/30645428/all-fiber-narrow-linewidth-ring-laser-with-continuous-and-large-tuning-range-based-on-microsphere-resonator-and-fiber-bragg-grating
#6
Ligang Huang, Pengfa Chang, Xiaoting Li, Wending Zhang, Yujia Li, Feng Gao, Fang Bo, Lei Gao, Wei Huang, Min Liu, Tao Zhu
We demonstrate an all-fiber single-longitudinal-mode (SLM) narrow-linewidth ring laser stabilized by a microsphere resonator and fiber Bragg gratings (FBGs) with a large continuous wavelength tuning range from 1540 nm to 1570 nm. In the experiment, stable lasing with a linewidth smaller than 5 kHz was obtained. The laser wavelength was linearly and continuously tuned in the range of 0.15 nm by increasing the pump power and discretely tuning with a step of 0.1 nm by stress-controlled FBGs. The tuning range of the proposed laser configuration was determined by the FBG, and the SLM state was ensured by the coupling between the few-mode tapered fiber and the microsphere, which was simpler in alignment than other ring lasers utilizing microresonators...
December 10, 2018: Optics Express
https://read.qxmd.com/read/30644869/generation-of-telecom-band-correlated-photon-pairs-in-different-spatial-modes-using-few-mode-fibers
#7
Cheng Guo, Jie Su, Zhenzhen Zhang, Liang Cui, Xiaoying Li
We experimentally demonstrate the production of photon pairs at 1555 nm in LP01 mode and at 1566.8 nm in LP11 mode, respectively, via the spontaneous intermodal four-wave mixing in a 100-m-long few-mode fiber. We achieve a coincidence to accidental-coincidence ratio of 28, which clearly indicates the existence of quantum correlation. We also discuss the contribution of spontaneous Raman scattering to the background noise of photon pairs. Our source of photon pairs, compatible with the low-loss multiplexing and de-multiplexing components for space division multiplexing optical fiber communication, can be used for generating higher-dimensional entanglement...
January 15, 2019: Optics Letters
https://read.qxmd.com/read/30499956/dynamic-mode-switchable-optical-vortex-beams-using-acousto-optic-mode-converter
#8
Jiafeng Lu, Linghao Meng, Fan Shi, Xiaomin Liu, Zhengqian Luo, Peiguang Yan, Liangjin Huang, Fufei Pang, Tingyun Wang, Xianglong Zeng, Pu Zhou
We propose a dynamic scheme to realize mode-switchable generation of LP11a/b modes and ±1-order orbital angular momentum (OAM) modes simultaneously, which are induced by an acoustically induced fiber grating driven by radio frequency modulation. LP11a/b mode degeneration in a few-mode fiber is induced by the geometric irregularity of optical fibers. A dual-wavelength resonance of mode coupling from LP01 to LP11a/b modes is found based on the combined effects of optical and acoustic birefringence. Within the configuration of continuous-wave intra-cavity laser output, we experimentally demonstrate a fast-switchable generation of LP11a/b modes and optical vortex beams with ±1-order OAM at a switching speed up to 4...
December 1, 2018: Optics Letters
https://read.qxmd.com/read/30470001/performance-of-mode-diversity-reception-of-a-polarization-division-multiplexed-signal-for-free-space-optical-communication-under-atmospheric-turbulence
#9
Manabu Arikawa, Toshiharu Ito
We investigated the performance of mode diversity reception of a polarization-division-multiplexed (PDM) signal with few-mode-fiber (FMF) coupling for high-speed free-space optical communications under atmospheric turbulence. Optical propagation through eigenmodes of a FMF yields coupling between different linearly polarized (LP) modes in orthogonal polarizations, which causes power imbalance and loss of the orthogonality of multiplexed signals within each individual LP mode. Due to this phenomenon, the architecture of mode diversity combining affects the receiver performance...
October 29, 2018: Optics Express
https://read.qxmd.com/read/30469672/few-mode-fiber-true-time-delay-lines-for-distributed-radiofrequency-signal-processing
#10
Rubén Guillem, Sergi García, Javier Madrigal, David Barrera, Ivana Gasulla
We report, for the first time to our knowledge, distributed radiofrequency signal processing built upon true time delay operation on a step-index few-mode fiber. Two 3-sample configurations with different time delay properties are implemented over the same 60-meter 4-LP-mode fiber link. The inscription of a long period grating at a specific fiber position converts part of the LP01 mode into the LP02 , permitting sample time delay engineering. Delay line performance is experimentally demonstrated when applied to radiofrequency signal filtering, example of fiber-distributed processing functionality exhibiting one order or magnitude gain in terms of compactness...
October 1, 2018: Optics Express
https://read.qxmd.com/read/30469642/distributed-acoustic-sensor-based-on-a-two-mode-fiber
#11
Mengmeng Chen, Ali Masoudi, Francesca Parmigiani, Gilberto Brambilla
A distributed optical fiber dynamic strain sensor also known as a distributed acoustic sensor (DAS) based on two-mode fiber is demonstrated. By using φ-OTDR interrogation technique, the backscattered light from higher order modes can be used to fully quantify vibrations along the sensing fiber. In addition, by combining the results obtained from different modes, 2.52dB improvement in noise floor is achieved. These results confirm that few-mode fibers can be used for DAS applications.
September 17, 2018: Optics Express
https://read.qxmd.com/read/30469617/dynamic-characteristics-of-stimulated-raman-scattering-in-high-power-fiber-amplifiers-in-the-presence-of-mode-instabilities
#12
Rumao Tao, Hu Xiao, Hanwei Zhang, Jinyong Leng, Xiaolin Wang, Pu Zhou, Xiaojun Xu
Impact of mode instability on dynamic characteristics of stimulated Raman scattering in high power fiber amplifiers has been studied for the first time, which reveals another characterization of mode instability from the aspect of optical spectrum. It shows that, after the onset of mode instability, the measured light spectrums, especially the Raman light spectrums, are different from those without mode instability, which become burr-like. As mode instability evolves into different stages, the intensity of stimulated Raman scattering effects as laser power increasing also behaves differently...
September 17, 2018: Optics Express
https://read.qxmd.com/read/30462019/coupling-ultrafast-laser-pulses-into-few-mode-optical-fibers-a-numerical-study-of-the-spatiotemporal-field-coupling-efficiency
#13
Zhe Guang, Yani Zhang
Few-mode optical fibers have been widely used in applications such as data transmission and laser amplification. The coupling of laser beams into such fibers is important because it determines the fiber mode contents, which influence the beam quality, laser amplification efficiency, and appropriate distortion control methods. Ultrafast lasers, as a widely used type of laser source for intense-field applications, can generate pulses with broad spectra and varying phases, adding complexity to the fiber mode coupling problem...
November 20, 2018: Applied Optics
https://read.qxmd.com/read/30461876/simultaneous-measurement-of-mode-dependent-loss-and-mode-coupling-in-few-mode-fibers-by-analyzing-the-rayleigh-backscattering-amplitudes
#14
Feng Liu, Guijun Hu, Congcong Song, Weicheng Chen, Cuiguang Chen, Jiake Chen
In this paper, we propose and experimentally demonstrate a nondestructive method for simultaneously measuring the mode-dependent loss (MDL) and mode coupling (MC) in few-mode fibers (FMFs). The method is based on analyzing the Rayleigh backscattering amplitudes obtained with an optical time domain reflectometer (OTDR). The experimental results show that, in about 4 km six-mode FMF, the MDL and MC values are 0.132 dB and -23.13  dB/km between LP01 and LP11a , 0.176 dB and -23.73  dB/km between LP01 and LP11b , 0...
October 20, 2018: Applied Optics
https://read.qxmd.com/read/30417035/highly-parallel-interferometric-diffusing-wave-spectroscopy-for-monitoring-cerebral-blood-flow-dynamics
#15
Wenjun Zhou, Oybek Kholiqov, Shau Poh Chong, Vivek J Srinivasan
Light-scattering methods are widely used in soft matter physics and biomedical optics to probe dynamics in turbid media, such as diffusion in colloids or blood flow in biological tissue. These methods typically rely on fluctuations of coherent light intensity, and therefore cannot accommodate more than a few modes per detector. This limitation has hindered efforts to measure deep tissue blood flow with high speed, since weak diffuse light fluxes, together with low single-mode fiber throughput, result in low photon count rates...
2018: Optica
https://read.qxmd.com/read/30411714/few-layer-bismuthene-for-femtosecond-soliton-molecules-generation-in-er-doped-fiber-laser
#16
Chong Wang, Lu Wang, Xiaohui Li, Wenfeng Luo, Tianci Feng, Ying Zhang, Penglai Guo, Yanqi Ge
Bismuthene, a mono-elemental two-dimensional material with a novel kind of few-layer structure purely consisting of bismuth, has been predicted to have a prominent optical response and enhanced stability in theory. In this paper, few-layer bismuthene is employed as the saturable absorber. The mode-locker is fabricated by dropping bismuthene on a microfiber in a passively mode-locked, Er-doped fiber laser. The single pulse can be obtained at 122.1 mW, with 621.5 fs pulse duration at 1557.5 nm central wavelength, 10...
January 11, 2019: Nanotechnology
https://read.qxmd.com/read/30325397/2d-bismuthene-fabricated-via-acid-intercalated-exfoliation-showing-strong-nonlinear-near-infrared-responses-for-mode-locking-lasers
#17
Qi-Qi Yang, Rui-Tong Liu, Chao Huang, Yi-Fan Huang, Lin-Feng Gao, Bing Sun, Zhi-Peng Huang, Lei Zhang, Chen-Xia Hu, Ze-Qi Zhang, Chun-Lin Sun, Qiang Wang, Yu-Long Tang, Hao-Li Zhang
The rediscovery of black phosphorus (BP) has expanded the 2D family into Group 15 (Nitrogen Group) elements, among which bismuthene is the latest member with extraordinary opto-electronic, catalytic and biocompatible properties and potential as a 2D topological insulator. However, bulk Bi is not easily mechanically exfoliated as its counterpart of BP. Thus, to date, the reports on 2D Bi fabrication are rare, and investigations on its nonlinear optical properties are even less. Herein, we rationally designed a new strategy combining acid-interaction and liquid exfoliation to successfully transform metal bulk Bi into few-layer semiconductor, which resulted in unseen opto-electronic properties, such as tunable nonlinear responses all the way to the near-infrared (NIR) region...
December 7, 2018: Nanoscale
https://read.qxmd.com/read/30272737/theory-of-thermo-optic-instabilities-in-dual-core-fiber-amplifiers
#18
Jesper Lægsgaard, Federica Poli, Annamaria Cucinotta, Stefano Selleri
A coupled-mode theory for nonlinear mode coupling by the thermo-optic effect, originally developed for single-core fiber amplifiers, is applied to the case of dual-core amplifiers. It is shown that a non-phase-matched coupling term, which is usually irrelevant in single-core amplifiers, can strongly affect the mode stability when the coupling length between supermodes exceeds a few centimeters. The phase-mismatched coupling can lead to a strongly reduced instability threshold and static deformation effects for a range of intermediate coupling lengths...
October 1, 2018: Optics Letters
https://read.qxmd.com/read/30258667/beyond-backscattering-optical-neuroimaging-by-brad
#19
Pablo Eugui, Antonia Lichtenegger, Marco Augustin, Danielle J Harper, Martina Muck, Thomas Roetzer, Andreas Wartak, Thomas Konegger, Georg Widhalm, Christoph K Hitzenberger, Adelheid Woehrer, Bernhard Baumann
Optical coherence tomography (OCT) is a powerful technology for rapid volumetric imaging in biomedicine. The bright field imaging approach of conventional OCT systems is based on the detection of directly backscattered light, thereby waiving the wealth of information contained in the angular scattering distribution. Here we demonstrate that the unique features of few-mode fibers (FMF) enable simultaneous bright and dark field (BRAD) imaging for OCT. As backscattered light is picked up by the different modes of a FMF depending upon the angular scattering pattern, we obtain access to the directional scattering signatures of different tissues by decoupling illumination and detection paths...
June 1, 2018: Biomedical Optics Express
https://read.qxmd.com/read/30213047/passive-q-switching-by-cr-4-yag-saturable-absorber-of-buried-depressed-cladding-waveguides-obtained-in-nd-doped-media-by-femtosecond-laser-beam-writing
#20
Gabriela Croitoru Salamu, Nicolaie Pavel
We report on laser performances obtained in Q-switch mode operation from buried depressed-cladding waveguides of circular shape (100 μm diameter) that were inscribed in Nd:YAG and Nd:YVO₄ media by direct writing with a femtosecond laser beam. The Q-switch operation was realized with a Cr4+ :YAG saturable absorber, aiming to obtain laser pulses of moderate (few μJ) energy at high (tens to hundreds kHz) repetition rate. An average power of 0.52 W at 1.06 μm consisting of a train of pulses of 7.79 μJ energy at 67 kHz repetition rate, was obtained from a waveguide realized in a 4...
September 12, 2018: Materials
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