2020

• Record 373 of
  
  Title:Compact optical module to generate arbitrary vector vortex beams
  
  Author(s):Zhou, Yuan(1,2); Li, Xing(1,2); Cai, Yanan(1,2); Zhang, Yanan(1,2); Yan, Shaohui(1); Zhou, Meiling(1); Li, Manman(1); Yao, Baoli(1,2)
  Source: Applied Optics  Volume: 59  Issue: 28  DOI: 10.1364/AO.401184  Published: October 1, 2020  
  Abstract:We demonstrated a compact optical module that is capable of efficiently generating vector vortex beams (VVB). With this device, a linearly polarized input beam can be converted into a vector beam with arbitrary spatial polarization and phase distributions, accompanied by an energy utilization up to 61%. Equally important, the area utilization of the spatial light modulator, a key component in the device, is as high as 65.5%. With the designed vector-vortex-beam-generation module, several types of VVBs with different vortex topological charges and spatial polarization distributions were created experimentally. This device may find applications in optical tweezers, laser machining, and so on. © 2020 Optical Society of America
  Accession Number: 20204209364730
• Record 374 of
  
  Title:2D molybdenum carbide (Mo2C)/fluorine mica (FM) saturable absorber for passively mode-locked erbium-doped all-fiber laser
  
  Author(s):Liu, Sicong(1); Wang, Yonggang(1,2); Lv, Ruidong(1); Wang, Jiang(1); Wang, Huizhong(1); Wang, Yun(1); Duan, Lina(3)
  Source: Nanophotonics  Volume: 9  Issue: 8  DOI: 10.1515/nanoph-2020-0019  Published: August 1, 2020  
  Abstract:As a new member of saturable absorber (SA), molybdenum carbide (Mo2C) has some excellent optical properties. Herein, we report a new type of Mo2C/fluorine mica (FM) SA device. Uniform and compact Mo2C films were deposited on the FM by magnetron sputtering method. In order to increase the laser damage threshold, an additional protective layer of silicon oxide was deposited on the Mo2C. The FM is a single-layer structure of 20 μm, and its high elasticity makes it not easy to fracture. The transmission rate of FM is as high as 90% at near infrared wavelength. FM has better heat dissipation and softening temperature than organic composite materials, so it can withstand higher laser power without being damaged. In this work, Mo2C/FM SA was cut into small pieces and inserted into erbium-doped fiber laser to achieve mode-locked operation. The pulse duration and average output power of the laser pulses were 313 fs and 64.74 mW, respectively. In addition, a 12th-order sub-picosecond harmonic mode-locking was generated. The maximum repetition rate was 321.6 MHz and the shortest pulse duration was 338 fs. The experimental results show that Mo2C/FM SA is a broadband nonlinear optical mode-locker with excellent performance. © 2020 Yonggang Wang et al., published by De Gruyter, Berlin/Boston.
  Accession Number: 20203209017100
• Record 375 of
  
  Title:Recent advances in high-power continuous-wave ytterbium-doped fiber lasers
  
  Author(s):Dang, Wen-jia(1); Li, Zhe(2); Li, Yu-ting(1); Lu, Na(1); Zhang, Lei(1); Tian, Xiao(1); Yang, Hui-hui(1)
  Source: Chinese Optics  Volume: 13  Issue: 4  DOI: 10.37188/CO.2019-0208  Published: August 1, 2020  
  Abstract:High power continuous-wave ytterbium-doped fiber lasers have unique advantages such as high electro-optical efficiency, excellent beam quality and good thermal management. For these reasons, these fiber lasers are widely used in industrial processing, national defense and military, and scientific research. However, their non-linear and thermal effects at high-power conditions limit the further improvement of their output power. In this paper, the formation mechanism and corresponding suppression methods of stimulated raman scattering and thermally induced mode instability are analyzed. We hope that these analyses can provide some reference for the design and integration of high-power fiber laser systems. The research results for overcoming these limited factors introduced since 2015 are then discussed in detail. This paper is concluded by predicting the development prospects of high-power continuous-wave ytterbium-doped fiber lasers. Copyright ©2020 Chinese Optics. All rights reserved.
  Accession Number: 20203609123341
• Record 376 of
  
  Title:Cascaded few-mode fiber down-taper modal interferometers and their application in curvature sensing
  
  Author(s):Chen, Enqing(1,2); Dong, Bo(1,2,3); Li, Yang(1,2); Wang, Xiaoli(1,2); Zhao, Yudi(1); Xu, Wei(1,2); Zhao, Wei(1,2,3); Wang, Yishan(1,2)
  Source: Optics Communications  Volume: 475  Issue:   DOI: 10.1016/j.optcom.2020.126274  Published: 15 November 2020  
  Abstract:Few-mode fiber modal interferometers (MIs) based on cascaded fiber down-tapers and their application in curvature sensing are presented. Cascaded fiber down-taper structure can help excite more higher-order cladding modes to construct the inter-modal interference with the core mode. However, with the increase of the cascaded number of the fiber down-tapers, the curvature sensitivity of the MI is decreased accordingly. This provides a new way to control the curvature sensitivity of such device by cascading fiber down-tapers. Experimental results show that compared with the two down-tapers based MI, the curvature sensitivity of the three down-tapers one reduced by 1.64 times while the four down-tapers one reduced by 5.82 times. © 2020 Elsevier B.V.
  Accession Number: 20203008961607
• Record 377 of
  
  Title:Research on ultra-smooth collimation separation of silicon wafer by multiple lasers
  
  Author(s):Youwang, Hu(1); Ming, Li(2); Qinqin, Xie(1); Xiaoyan, Sun(1)
  Source: Proceedings - 2020 3rd International Conference on Electron Device and Mechanical Engineering, ICEDME 2020  Volume:   Issue:   DOI: 10.1109/ICEDME50972.2020.00109  Published: May 2020  
  Abstract:Micro-cracks are prefabricated on the surface of the silicon wafer, and laser thermal cracking is used to dice the silicon wafer, which can greatly reduce the surface roughness of the cross section of the wafer, improve the straightness after cutting, and achieve high-quality dicing of silicon wafers. This is a new dicing technology with huge application value. © 2020 IEEE.
  Accession Number: 20202908946740
• Record 378 of
  
  Title:Screen printing of upconversion NaYF4:Yb3+/Eu3+ with Li+ doped for anti-counterfeiting application
  
  Author(s):Li, Dongdong(1); Mo, Jianye(1); Wang, Chong(1); Liu, Wei(1); Ge, Haibo(1); Han, Dongdong(1); Hao, Aihua(1); Chai, Baoyu(1); She, Jiangbo(2)
  Source: Chinese Optics Letters  Volume: 18  Issue: 11  DOI: 10.3788/COL202018.110501  Published: November 10, 2020  
  Abstract:Li ions affect the upconversion efficiency by changing the local crystal field of the luminescent center. Herein, in order to improve the upconversion efficiency of NaYF4:Yb3+/Eu3+, a series of NaYF4:Yb3+/Eu3+ micro-particles with different Li+ doping concentrations were synthesized by the hydrothermal synthesis method, respectively. Firstly, the structure and morphology of NaYF4:Yb3+/Eu3+ upconversion micro-particles (UCMPs) with different doping concentrations were analyzed by X-ray diffraction and a scanning electron microscope (SEM). SEM results show that the UCMPs are not only highly crystallized, but also have hexagons with different Li+ concentrations of NaYF4:Yb3+/Eu3+. X-ray diffraction shows that the crystal field around Eu3+ changes with the increase of Li+ concentration. Then, the fluorescence spectrum of NaYF4:Yb3+/Eu3+ was studied under the irradiation of a 980 nm laser. The results show that the fluorescence intensity of NaYF4:Yb3+/Eu3+ with 2% Li+ is the strongest, which is twice the intensity of NaYF4:Yb3+/Eu3+ without Li+. Finally, the fluorescence imaging analysis of NaYF4:Yb3+/Eu3+ with 2% Li+ concentration was carried out. The UCMPs are used to screen printing to evaluate the imaging effect on different sample surfaces. The results show NaYF4:Yb3+/Eu3+ (with 2% Li+) has great application prospects in anti-counterfeiting recognition. © 2020 Chinese Optics Letters.
  Accession Number: 20210609892144
• Record 379 of
  
  Title:Full-polarization wavefront shaping for imaging through scattering media
  
  Author(s):Li, Runze(1); Peng, Tong(1); Zhou, Meiling(1); Yu, Xianghua(1); Min, Junwei(1); Yang, Yanlong(1); Yao, Baoli(1)
  Source: Applied Optics  Volume: 59  Issue: 17  DOI: 10.1364/AO.391909  Published: June 10, 2020  
  Abstract:The scattering effect occurring when light passes through inhomogeneous-refractive-index media such as atmosphere or biological tissues will scramble the light wavefront into speckles and impede optical imaging. Wavefront shaping is an emerging technique for imaging through scattering media that works by addressing correction of the disturbed wavefront. In addition to the phase and amplitude, the polarization of the output scattered light will also become spatially randomized in some cases. The recovered image quality and fidelity benefit from correcting as much distortion of the scattered light as possible. Liquid-crystal spatial light modulators (LC-SLMs) are widely used in the wavefront shaping technique, since they can provide a great number of controlled modes and thereby high-precision wavefront correction. However, due to the working principle of LC-SLMs, the wavefront correction is restricted to only one certain linear polarization state, resulting in retrieved image information in only the right polarization, while the information in the orthogonal polarization is lost. In this paper, we describe a full-polarization wavefront correction system for shaping the scattered light wavefront in two orthogonal polarizations with a single LC-SLM. The light speckles in both polarizations are corrected for retrieval of the full polarization information and faithful images of objects. As demonstrated in the experiments, the focusing intensity can be increased by full-polarization wavefront correction, images of objects in arbitrary polarization states can be retrieved, and the polarization state of the object's light can also be recognized. © 2020 Optical Society of America
  Accession Number: 20202508845386
• Record 380 of
  
  Title:Breathing process monitoring with a biaxially oriented polypropylene film based fiber Fabry–Perot sensor
  
  Author(s):Li, Yang(1,2); Dong, Bo(1,2,3); Chen, Enqing(1,2); Wang, Xiaoli(1,2); Zhao, Yudi(1,2); Zhao, Wei(1,2,3); Wang, Yishan(1,2)
  Source: Optics Communications  Volume: 475  Issue:   DOI: 10.1016/j.optcom.2020.126292  Published: 15 November 2020  
  Abstract:The breathing process monitoring with a biaxially oriented polypropylene (BOPP) film based fiber Fabry–Perot (F–P) sensor is presented. The fiber F–P sensor is fabricated with 3-D printing technology and fixed on a medical respirator for breathing process monitoring. Due to the low Young's modulus of the BOPP film and its thinner thickness, the breathing sensor shows the high pressure sensitivity of -0.581 nm/Pa. By monitoring its intensity response to the pressure induced by breathing, the breathing process can be monitored accurately, including respiratory waveform, respiratory rate, inspiratory duration and amplitude, expiratory duration and amplitude, and inspiratory and expiratory rhythm. Since the sensor is all fiber design with the inherent advantages of small size, anti-electromagnetic interference, green environmental protection, pollution-free and no harm to body, it is expected to be widely used in respiratory disease monitoring. © 2020 Elsevier B.V.
  Accession Number: 20203008965436
• Record 381 of
  
  Title:Polarization-dependent micro-structure fabrication with direct femtosecond laser writing on plastic polarizer films
  
  Author(s):Yu, Xianghua(1); Liu, Chao(1); Lei, Ming(1); Yan, Shaohui(1); Peng, Tong(1); Dan, Dan(1); Yao, Baoli(1)
  Source: Optics Letters  Volume: 45  Issue: 9  DOI: 10.1364/OL.390349  Published: May 1, 2020  
  Abstract:Iodine-doped polyvinyl alcohol (IDPVA) film has been widely used as a plastic polarizer due to its great linear dichroism. We found that the anisotropic character of the plastic polarizer can be permanently damaged upon exposure of high intensity femtosecond laser pulses. This process is a two-photon-induced chemical reaction and denominated as two-photon-induced isotropy (TPII). The TPII effect can form a high polarization contrast on the base of the original IDPVA films. With this property, polarization-sensitive diffractive optical elements are fabricated in IDPVA films. The low cost of the IDPVA film and the high polarization contrast of TPII make it a promising new candidate for femtosecond laser fabrication of polarization-selective optical elements. © 2020 Optical Society of America.
  Accession Number: 20202008655223
• Record 382 of
  
  Title:Retrieval of non-sparse objects through scattering media beyond the memory effect
  
  Author(s):Zhou, Meiling(1); Li, Runze(1); Peng, Tong(1); Pan, An(1); Min, Junwei(1); Bai, Chen(1); Dan, Dan(1); Yao, Baoli(1)
  Source: Journal of Optics (United Kingdom)  Volume: 22  Issue: 8  DOI: 10.1088/2040-8986/aba0fc  Published: August 2020  
  Abstract:Optical imaging through scattering media is commonly constrained to sparse objects and the optical memory effect. To solve the problems, a method based on the combination of ptychography and the shower-curtain effect is presented here to achieve the retrieval of non-sparse samples through scattering media beyond the memory effect. The phase disturbance introduced by scattering media can be neglected based on the shower-curtain effect, and also the field-of-view can be extended via the ptychography. Results of the retrieval of hair-follicle cell from human skin demonstrate the effectiveness and feasibility of the proposed method for static and dynamic scattering media with the extended field-of-view to be 3.2 mm 3.2 mm. The present work may be an approach for imaging through deep biological tissues. © 2020 IOP Publishing Ltd.
  Accession Number: 20204309383965
• Record 383 of
  
  Title:Phase-sensitive amplification of a QPSK signal using a dispersion engineered silicon-graphene oxide hybrid waveguide
  
  Author(s):Chen, Zhihua(1,3); Liu, Hongjun(1,2); Wang, Zhaolu(1); Huang, Nan(1)
  Source: Applied Optics  Volume: 59  Issue: 7  DOI: 10.1364/AO.382778  Published: March 1, 2020  
  Abstract:We numerically investigate phase-sensitive amplification of a quadrature phase shift keying (QPSK) signal in a 35 μm dispersion engineered silicon-graphene oxide hybrid waveguide. The four-wave mixing efficiency is effectively enhanced by exploiting the ultrahigh Kerr nonlinearity and low loss of graphene oxide in the ultrawide wavelength range. A new structure of dispersion flat silicon-graphene oxide hybrid waveguide is proposed and used to achieve the phase regeneration of a QPSK signal using a dual-conjugated-pump degenerate scheme. The phasedependent gain and phase-to-phase transfer functions are calculated to analyze the properties of a phase-sensitive amplifier (PSA). The constellation diagrams of the QPSK signal and the error vector magnitude are used to assess the regeneration capacity. The simulation results show that the proposed PSA with a good phase noise squeezing capability has potential applications in all-optical signal processing. © 2020 Optical Society of America.
  Accession Number: 20201008269827
• Record 384 of
  
  Title:Kilowatt-level tunable all-fiber narrowband superfluorescent fiber source with 40 nm tuning range
  
  Author(s):Li, Zhe(1,3); Li, Gang(1,3); Gao, Qi(1,3); Wu, Peng(1,3); She, Shengfei(1,3); Wang, Zhaolu(1); Huang, Nan(1); Sun, Chuandong(1); Gao, Wei(1,3); Ju, Pei(1,3); Liu, Hongjun(1,2)
  Source: Optics Express  Volume: 28  Issue: 7  DOI: 10.1364/OE.387405  Published: March 30, 2020  
  Abstract:In this study, we presented a high-power widely tunable all-fiber narrowband superfluorescent fiber source (SFS) by employing two tunable bandpass filters and three amplifier stages. More than 935 W output power is achieved, with a slope efficiency of >75% and a beam quality factor of M2=1.40. The tuning of the narrowband SFS ranges from ∼1045 nm to ∼1085 nm with a full width at half maximum linewidth of less than 0.71 nm. The tunable narrowband SFS stably operates without the influence of parasitic oscillation and self-pulsing effects under maximum power. To the best of our knowledge, this study is the first to demonstrate a widely tunable all-fiber narrowband SFS around 1 μm wavelength region with output power reaching kilowatt-level. © 2020 Optical Society of America.
  Accession Number: 20201508392445