2019
2019
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Record 469 of
Title:Optimum design for comb-index core fiber with large mode area
Author(s):Miao, Xiaofang(1,2); Wu, Peng(1,2); Zhao, Baoyin(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 48 Issue: 9 DOI: 10.3788/IRLA201948.0918005 Published: September 25, 2019Abstract:The wave-guide structure of the large mode area fiber with a comb-index core was optimized by adding a high refractive index platform in the outer layer of the fiber core, which provided a performance promotion on the parameters of mode field area, mode field distribution and bending resistance. The simulation results show that the optimized refractive index distribution increases the fiber's mode field area by more than 700 μm2, and reduces bending loss of the fundamental mode from 6 dB/m to 0.1 dB/m at the same bending radius compared with the original comb-index distribution. Moreover, the mode field distributions including Gauss-like distribution, flattened distribution and hollow distribution, can be obtained by simply modulating the refractive-index parameters of the outermost platform, which may meet the needs of special laser processing industry. ? 2019, Editorial Board of Journal of Infrared and Laser Engineering. All right reserved.Accession Number: 20194507622961 -
Record 470 of
Title:X-ray transmission characteristics and potential communication application in plasma region
Author(s):Li, Yao(1,2); Su, Tong(1,2); Lei, Fan(3); Xu, Neng(1,2); Sheng, Li-Zhi(1); Zhao, Bao-Sheng(1)Source: Wuli Xuebao/Acta Physica Sinica Volume: 68 Issue: 4 DOI: 10.7498/aps.68.20181973 Published: February 20, 2019Abstract:When a supersonic spacecraft enters into the atmosphere of earth, part of the spacecraft's kinetic energy changes into thermal energy, thus causing the air surrounding the craft to be heated and compressed. As a result, the temperature near the surface may reach several thousands of kelvins, which leads the surface materials to be ionized and form a plasma sheath around the vehicle. This plasma layer has an electron density ranging from 1015m-3 to 1020m-3, and may interrupt the radio communication signal between the re-entry vehicle and ground-based stations, which is known as ‘communication blackout’. According to the radio attenuation measurement (RAM) experiments carried out by NASA(National Aeronautics and Space Administration) in the 1970s, the duration time of communication blackout ranges from 4 to 10 minutes in an altitude range from 40 km to 100 km. Communication blackout has puzzled aerospace industry for several decades, and has not yet been completely resolved. Due to this, it becomes necessary to understand the causes of communication blackout and the methods for its mitigation. Compared with other communication methods, x-ray communication(XCOM) has the advantages of short carrier wavelength and high photon energy, as well as strong ability to resist anti-interference, thus being able to open a novel way to solve this long-lasting unresolved problem. In this paper, to begin with, we analyze the transmission coefficiencies under different plasma electron densities and collision frequencies based on Wentzel Kramers Brillouin (WKB) approximation method. The simulation results indicate that the x-ray carrier is not influenced by the reentry plasma sheath. After that, a plasma source based on glow discharge is used to verify the mathematical model. The non-magnetized unobstructed plasma region is φ200 mm×180 mm, which can be used for simulating plasma sheath near the reenter spacecraft. Then the transmission coefficiency, energy spectrum similarity and energy spectrum peak offset under different x-ray energy, x-ray flow and plasma electron density are firstly analyzed. Experimental results indicate that plasma can lead the x-ray signal to be attenuated to a certain extent, the increase of plasma electron density will cause higher attenuation. However, with a higher signal x-ray energy and x-ray flow, the XCOM could achieve less attenuation in the re-enter plasma layer. When the plasma electron density ranges from 6×1016/m3 to 1.2×1017/m3, 1.34 Mcps signal x-ray photons’ flow with 20 kV anode voltage would achieve more than a 95% transmission efficiency. Also, the spectrum of x-ray signal can obtain more than 95.5% similarity and the peak offset is less than 1.3% after passing the plasma sheath. Subsequently, based on the original mathematic model and experimental results, considering the free-free absorption, free-bound absorption, bound-bound absorption and scattering effect of x-ray photons in plasma, the x-ray transmission characteristics are optimized to make simulation results well consistent with the experiment results. Finally, an MCNP (Monte Carlo N Particle) transport simulation is used to analyze the feasibility of XCOM in blackout region, which indicates that the energy range 15-25 keV is the suitable to achieve the XCOM in adjacent space, and the relation of potential transmitting speed with bit error is calculated. Theoretically, the XCOM can achieve about 1.3 Mbps communication speed in blackout region. In summary, these theoretical and experimental results indicate that the XCOM is a potential and novel method to solve the blackout communication problems. ? 2019 Chinese Physical Society.Accession Number: 20191906900384 -
Record 471 of
Title:Indium selenide as a saturable absorber for a wavelength-switchable vector-soliton fiber laser
Author(s):Wang, Guomei(1,2); Chen, Guangwei(1,2); Li, Wenlei(1,2); Zhang, Wenfu(1,2); Zeng, Chao(1,2); Zhao, Wei(1,2)Source: Optical Materials Express Volume: 9 Issue: 2 DOI: 10.1364/OME.9.000449 Published: February 1, 2019Abstract:We experimentally demonstrate that indium selenide (In2Se3), a III-VI group layered chalcogenide compound, can be used as a saturable absorber (SA) for a wavelengthswitchable vector-soliton fiber laser. The modulation depth of the In2Se3-based SA (In2Se3- SA), fabricated by incorporating In2Se3 nanosheets with polyvinyl alcohol, is up to 14%. By inserting the In2Se3-SA into fiber laser, solitons switched at wavelengths of ~1558 and ~1530 nm, with the duration of ~1.88 and ~1.76 ps respectively, can be obtained by adjusting the polarization controller and the pump power. Further investigations demonstrate that the achieved solitons are polarization-locked vector conventional solitons, which reveals that the In2Se3 can serves as a polarization-independent SA. The results indicate that the III-VI group chalcogenide compounds, including In2Se3, could be developed as an alternative for ultrafast pulse generations, particularly, vector-soliton pulse. ? 2019 Optical Society of America.Accession Number: 20190406427389 -
Record 472 of
Title:Underwater LED Communication Based on Secondary Light Distribution with Total Internal Reflection Lens
Author(s):Wang, Tao(1,2); Han, Biao(1); Shi, Kui(1); Wu, Yafeng(1); Zheng, Yunqiang(1); Y., Han; X., Xie; W., Wang; J., MengSource: Guangxue Xuebao/Acta Optica Sinica Volume: 39 Issue: 8 DOI: 10.3788/AOS201939.0806001 Published: August 10, 2019Abstract:Blue-green LED communication is considered to be an effective means to solve the problem of underwater short-distance high-speed wireless data transmission. However, as LED divergence angle is usually quite large, the geometric loss is great in such communication link, which would reduce the communication distance. Aiming at this problem, a method is proposed to compress the emitter angle of underwater LED array light source with the total internal reflection (TIR) lens in this work. First, the divergence angle of LED array source is compressed from 130°to 7°. Then, a communication transmitter prototype is developed with the source, and a test system is built in a large tank to test the performance of the transmitter. The experimental results show that the communication prototype designed in this paper can support a maximum transmission rate of 23 Mbit/s when the underwater transmission distance is 16.6 m. Compared with the case without TIR lens, the maximum transmission distance increases 9.3 m at the same rate. It shows that the method of secondary light distribution with TIR lens can effectively reduce the transmitter's divergence angle and the link loss of transmission system, enhance the transmission capacity of communication system. It provides a new technical means for improving the transmission performance of underwater LED communication. ? 2019, Chinese Lasers Press. All right reserved.Accession Number: 20193607409765 -
Record 473 of
Title:Imaging property analysis of segmented mirror
Author(s):Li, Yichao(1,2); Kang, Fuzeng(1); Wang, Hao(1,2)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 48 Issue: 1 DOI: 10.3788/IRLA201948.0118006 Published: January 25, 2019Abstract:Segmented errors have important influence on the image quantity of segmented mirror. The complex amplitude distribution of reflected lightwave corresponding to single segment was given based on the scalar diffraction theory. The analysis model which characterized the impact of segmented errors was established by processing the segmented errors through coordinate transformation method. The Point Spread Function (PSF) and Strehl Ratio (SR) curves corresponding to various segmented errors were got by numerical simulation. The results show that SR curves corresponding to piston errors are periodic. The SR curves corresponding to tip-tilt errors and segment gaps have same structures. The conclusion provides a support for the image quantity analysis of segmented mirror. ? 2019, Editorial Board of Journal of Infrared and Laser Engineering. All right reserved.Accession Number: 20191106621836 -
Record 474 of
Title:Glass preparing and integrating technology in X-ray grazing incidence optics
Author(s):Qiang, Pengfei(1,2); Su, Tong(1,2); Liu, Zhe(1); Li, Linsen(1,2); Li, Yao(1,2); Liu, Yong-An(1,2); Sheng, Lizhi(3)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11052 Issue: DOI: 10.1117/12.2522653 Published: 2019Abstract:Glass preparing and integrating technologies are important in construction of grazing incidence optics, and these vital process are corresponding to the concentrating efficiency directly. Thermal slump glass under pressure supplied by stainless cloth with mass has been shown in this paper, and we obtained a below 1 nm roughness by coating Ir on slump glass segments. Then, A novel 6 dimensional integrating system for grazing incidence optics was developed to assemble all segments together, carbon ribs and epoxy were applied in the integrating process to make fragile glass segments stable. Finally, a glass-carbon-epoxy structure grazing incidence optics was developed and focal spot with diameter of 6 mm was obtained with parallel light. This kind of grazing incidence optics is supposed to concentrate large area X-ray photons to small area for reducing cost on space applications. ? 2019 SPIE.Accession Number: 20190806535067 -
Record 475 of
Title:Single-photon reflectivity and depth imaging by continuous measurement of arrival time of photons
Author(s):Yan, Qiurong(1); Li, Dan(1); Wang, Yifan(1); Yang, Yibing(1); Tang, Linao(2); Wang, Yuhao(1)Source: IEEE Photonics Journal Volume: 11 Issue: 6 DOI: 10.1109/JPHOT.2019.2945989 Published: December 2019Abstract:We demonstrate a reflectivity and depth imaging Lidar system based on a novel photon arrival time measurement method. In this method, the arrival time of photons in a scanning position is continuously measured with a common starting point. The number of laser pulses is counted by a specially designed field programmable gate array (FPGA) control module as the coarse time of arrival photon. Time interval between arrival photon and the nearest coming laser pulse is measured by a time-correlated single-photon counting (TCSPC) module as the fine time of arrival photon. Using the system, not only the single-photon counting imaging can be realized, but also the first photon imaging, the first two photons imaging, etc. can be realized. A photon statistical model based on the doubly stochastic Poisson point processes, a time-gated filtering algorithm, and the reflectivity algorithm based on maximum likelihood estimation are derived. High-sensitivity reflectivity and depth imaging with a resolution of 512 × 512 pixels are achieved. The experimental results show that the horizontal spatial resolution is 2 mm, the vertical depth resolution is 5.375 cm, and the average number of photons per pixel is less than 1.3 photons. ? 2009-2012 IEEE.Accession Number: 20200207996686 -
Record 476 of
Title:Review of resolution enhancement technologies in quantitative phase microscopy
Author(s):Gao, Peng(1); Wen, Kai(1,2,3); Sun, Xueying(1); Yao, Baoli(2); Zheng, Juanjuan(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 48 Issue: 6 DOI: 10.3788/IRLA201948.0603007 Published: June 25, 2019Abstract:Quantitative Phase Microscopy (QPM), which combines phase imaging and optical microscopy, has been acting as a fast, non-destructive, and high-resolution methodology to measure the 3D morphology of reflective samples, as well as the inner structure or the refractive index of transparent samples. Similar to other diffraction-limited imaging systems, QPM suffers from the contradiction between spatial resolution and field of view (FOV). Therefore, how to achieve high spatial resolution in a large FOV has attracted a lot of attentions in the field of optical microscopy. In recent years, people utilized off-axis illumination, speckle illumination, structural illumination, and sub-pixel technology to synthesize a larger numerical aperture (SNA), and consequently enhanced the resolution of QPM. The resolution enhancement technologies of QPM were reviewed in this paper. The advantages and limitations of different methods were analyzed. ? 2019, Editorial Board of Journal of Infrared and Laser Engineering. All right reserved.Accession Number: 20193407357463 -
Record 477 of
Title:Sampling time adaptive single-photon compressive imaging
Author(s):Wang, Hui(1); Yan, Qiurong(1,2); Li, Bing(1); Yuan, Chenglong(1); Wang, Yuhao(1)Source: IEEE Photonics Journal Volume: 11 Issue: 3 DOI: 10.1109/JPHOT.2019.2912326 Published: June 2019Abstract:We propose a time-adaptive sampling method and demonstrate a sampling-time-adaptive single-photon compressive imaging system. In order to achieve self-adapting adjustment of sampling time, the theory of threshold of light intensity estimation accuracy is deduced. According to this threshold, a sampling control module, based on field-programmable gate array, is developed. Finally, the advantage of the time-adaptive sampling method is proved experimentally. Imaging performance experiments show that the time-adaptive sampling method can automatically adjust the sampling time for the change of light intensity of image object to obtain an image with better quality and avoid speculative selection of sampling time. ? 2019 IEEE.Accession Number: 20192106962661 -
Record 478 of
Title:Direct calculation of tightly focused field in an arbitrary plane
Author(s):Cai, Yanan(1,2); Wang, Zhaojun(1,2); Liang, Yansheng(1); Ren, Feifei(1,2); Yao, Baoli(1); Lei, Ming(1); Yan, Shaohui(1)Source: Optics Communications Volume: 450 Issue: DOI: 10.1016/j.optcom.2019.06.022 Published: 1 November 2019Abstract:The Debye–Wolfdiffraction integral is a powerful tool for computing the focused field of an illumination by a high numerical aperture (NA) objective lens. With the help of the fast Fourier Transform (FT) algorithm, this integral can be evaluated at a high processing speed. In general, the FT pair is the illumination field at the entrance pupil and the focused field in a transverse plane in the focal region, i.e., the xy-plane. To analyze the field distribution of special beams in a titled plane, conventional calculations require a stack of slices of fields in the xy-planes plane by plane. Here, we propose a modified FT-based diffraction integral algorithm that exhibits a direct FT connection between the illumination field and the field in an arbitrary plane in the focal volume. As a result, significant time saving is achieved with the proposed algorithm. The algorithm is verified by numerous simulations and should be helpful to quickly design holograms to shape complex focus used in holographic optical tweezers. ? 2019 Elsevier B.V.Accession Number: 20192507061282 -
Record 479 of
Title:Percussion drilling on nickel-based alloy with thermal barrier coatings using femtosecond laser
Author(s):Zhai, Zhaoyang(1,2,3); Wang, Wenjun(1,2,3); Mei, Xuesong(1,2,3); Li, Ming(4); Li, Xun(4)Source: Optik Volume: 194 Issue: DOI: 10.1016/j.ijleo.2019.163066 Published: October 2019Abstract:Femtosecond laser with wave length of 800 nm was used to perform percussion drilling experiment on nickel-based alloy with thermal barrier coatings (TBCs) in order to eliminate the damages caused by conventional drilling. Analysis of the experimental results indicated that short pulse duration and high peak power characteristics of femtosecond laser led to good processing effect on nickel-based alloy with TBCs. High quality array of holes with the taper of almost zero was generated, for which the inner diameter was 162 μm and the aspect ratio was 15:1. Femtosecond laser processing had little influence on elementary components and phase structure of coating. This study provides feasible technique involving the use of femtosecond laser for machining film cooling hole on nickel-based alloy with TBCs. ? 2019 Elsevier GmbHAccession Number: 20192907185127 -
Record 480 of
Title:Numerical Simulation of 2.8 μm Gain-Switched Er:ZBLAN Fiber Laser
Author(s):Luan, Kunpeng(1); Shen, Yanlong(1,2,3); Tao, Mengmeng(1); Zhu, Feng(1); Huang, Chao(1); Chen, Hongwei(1); Yi, Aiping(1)Source: Guangxue Xuebao/Acta Optica Sinica Volume: 39 Issue: 7 DOI: 10.3788/AOS201939.0714001 Published: July 10, 2019Abstract:This study demonstrates a simulation model of a 2.8 μm gain-switched Er:ZBLAN fiber laser by numerical simulation. The simulation results show that there exists an optimal transmittance of output mirror, resulting in an largest output power. The coupling efficiency has significant impacts on the pulse width, peak power, and pulse shape. Accordingly, the influence of the pump power on the pulse shape is calculated and discussed. A signal pulse appears during two pump periods with a weak pump, whereas several signal pulses appear during one pump period with a strong pump. To the best of our knowledge, calculation results, such as the influence of the coupling efficiency on the output power, pulse energy, and pulse shape and the weak signal consistent with pump period when the pump power is around the threshold, have not been reported in any experiment. This study shows that a stable gain-switched pulse output in a 2.8 μm Er:ZBLAN fiber laser can be achieved only with appropriate coupling efficiency and pump power. ? 2019, Chinese Lasers Press. All right reserved.Accession Number: 20193607400991