2021
2021
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Record 433 of
Title:Investigation on secondary electron emission characteristics of double-layer structures
Author(s):Wang, Dan(1); He, Yongning(1); Guo, Junjiang(2,3,4); Cai, Yahui(1); Mao, Zhangsong(1); Ye, Ming(1)Source: Journal of Applied Physics Volume: 129 Issue: 9 DOI: 10.1063/5.0023325 Published: March 7, 2021Abstract:Secondary electron (SE) emission (SEE) from material surfaces is a frequent phenomenon in space and vacuum environments. SEE modulation is important since it governs the performance of some devices such as electronic multipliers or induces some detrimental effects such as multipactors. Surface coating has been reported to modulate SEE effectively, whereas SEE behaviors of coating structures are not clearly understood yet, and the appropriate theory to describe SEE characteristics quantitatively for coating structures is less developed so far. Here, we have prepared four alumina coatings possessing various thicknesses to research the SEE characteristics of coating structures and have shown how the coating thickness affects the SEE behaviors. Besides, by considering coating/substrate as an ideal double-layer structure, we have derived several equations to describe the producing, transmitting, and escaping processes of excited inner SEs and finally constructed a unidimensional SEE model for double-layer structures. The model is applicable to reveal the dependence of trueSE yield (TSEY) on the top and bottom layers' physical properties and estimate TSEY proportions contributed by the top and bottom layers at random energy points. By employing the concept, SEE characteristics of Al2O3/Si, MgO/Si, and TiO2/Si double-layer structureshave been quantitatively interpreted. Moreover, the abnormal SEY curve with a double-hump shape, which is induced by the peak position distinction of SiO2/Si structures, can also be explained. This work is of great significance to comprehend TSEY modulating regularities of various double-layer structures applied in surface engineering. ? 2021 Author(s).Accession Number: 20211110075432 -
Record 434 of
Title:Analysis of corrected Cerenkov emission during electron radiotherapy by Monte Carlo method
Author(s):Li, Yi(1,2,4); Liu, Hongjun(1,3); Huang, Nan(1); Wang, Zhaolu(1); Zhang, Chunmin(2)Source: Applied Radiation and Isotopes Volume: 168 Issue: DOI: 10.1016/j.apradiso.2020.109481 Published: February 2021Abstract:Cerenkov emission during electron radiotherapy had been emerging as a new dose assessment approach for clinical radiotherapy and could be imaged through a standard commercial camera. The purpose of this work aimed to study the accuracy of corrected Cerenkov emission method during electron radiotherapy by Monte Carlo (MC) method. GAMOS MC software was used to model the physics of electron therapy and calculated dose and Cerenkov photon distribution in water phantom. Compared to ionization chamber and diode measurement, MC simulated dose discrepancy was less than 1% in percentage depth dose (PDD) curves and less than. 2% in crossline profile curves, which was acceptable for clinical criterion. Compared to ionization chamber dose measurement, MC simulated Cerenkov discrepancy was less than 2% in crossline profile distribution, which was acceptable for clinical criterion. However, the Cerenkov PDD curves tended to overestimate the dose at the build-up region and underestimate the dose at the remaining attenuation region. After increasing the Cerenkov distribution depth to 2–3 mm, the discrepancy became well within 1% at the remaining attenuation region, which was acceptable for clinical criterion. Therefore, corrected Cerenkov emission could be used to assess PDD accuracy and crossline profile accuracy during electron radiotherapy. ? 2020 Elsevier LtdAccession Number: 20204409417426 -
Record 435 of
Title:GaAs material photorefractive response time measurement based on spectral probe
Author(s):Yang, Qing(1); Yin, Fei(1,2); Wang, Tao(2); Gao, Guilong(2); He, Kai(2); Yan, Xin(2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11761 Issue: DOI: 10.1117/12.2586950 Published: 2021Abstract:The ultrafast all-optical solid-state framing camera(UASFC) technique is a new diagnostic method based on the semiconductor photorefractive effect. The ultra-fast response characteristics of this method are mainly determined by the response time of the semiconductor material's photorefractive index change. How to quickly and accurately measure the photorefractive index response time of semiconductor materials is an important step in the development of all-optical solid ultra-fast diagnostic chip. In this paper, the 100fs pulsed laser is divided into two beams. One of which is used as excitation light to generate pulsed X-ray source; the other beam is measured as a spectral probe light. Through the test of GaAs material, the response time of the refractive index change of GaAs material was less than 5ps, which laid a foundation for further optimization experiment and accurate measurement. ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.Accession Number: 20210509874615 -
Record 436 of
Title:The mutual influence between rare earth element doping and femtosecond laser-induced effects in Ga-As-Sb-S chalcogenide glass
Author(s):Liu, Lutao(1,2); Chen, Fengyi(3); Cui, Jian(1,2); Xiao, Xusheng(1); Xu, Yantao(1,2); Hou, Chaoqi(1,2); Cui, Xiaoxia(1,2); Guo, Haitao(1,2,4)Source: Ceramics International Volume: 47 Issue: 5 DOI: 10.1016/j.ceramint.2020.10.219 Published: March 1, 2021Abstract:Femtosecond laser-induced damage thresholds (LIDTs) of Ga0.8As29.2Sb10S60 glasses doped with gradient Tm3+ concentrations and the effects of laser-induced damage on the glass' luminescence properties were studied in this work. Tm3+ doping in the glass considerably decreased the LIDT, from 3394.8 to 1881.8 mJ/cm2, when the Tm3+ concentration increased from 0 to 5000 ppmw. This was related to the absorption of Tm3+ around the femtosecond laser's wavelength and microstructural changes caused by the Tm3+ doping. On the other hand, the femtosecond laser changed the glass matrix's elemental distribution and microstructure. Although the laser damaged the glass, the luminescence properties were barely affected. Based on the changes, femtosecond laser damage mechanism of chalcogenide glass doped with rare earth element was firstly proposed. ? 2020Accession Number: 20204709521265 -
Record 437 of
Title:Application and Research of NaYF4:Yb3+/Eu3+ Upconverting Luminescent Micro-Nano Particles in Anti-Counterfeiting Identification
Author(s):Wang, Chong(1); Mo, Jian-Ye(1,2); Li, Dong-Dong(1); She, Jiang-Bo(2); Liu, Zhen(2)Source: Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis Volume: 41 Issue: 5 DOI: 10.3964/j.issn.1000-0593(2021)05-1525-05 Published: May 2021Abstract:Rare earth doped upconversion luminescent micro-nano particles have great application prospects in anti-counterfeit identification. First of all, in the article NaYF4:Yb3+/Eu3+ micro-nano particles prepared by hydrothermal synthesis method, The size, morphology and crystallinity of NaYF4:Yb3+/Eu3+ micro-nano particles were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope, and the luminescence properties of NaYF4:Yb3+/Eu3+ micro-nano particles were analyzed using a 980 nm pump source; Secondly, NaYF4:Yb3+/Eu3+ micro-nano particles and alcohol were mixed in a certain proportion to make a screen printing agent and combined with a network-customized screen template, different anti-counterfeit patterns were printed on the paper. After air drying, the words were exposed to a 980 nm laser and camera were used to study it. Finally, the printed words were divided into two parts, one was stored indoors at a constant temperature of 25℃, and the other was stored in the outdoor natural environment in January in winter. The storage locations are all Xi'an. After one week, in different environments the words were again tested with the same experimental instruments for imaging. The experiment and test results show that the diffraction peak of NaYF4:Yb3+/Eu3+ micro-nano particles is a completely consistent standard card of NaYF4, and no other impurities are generated. In this experiment, The synthesized micro-nano particles are all hexagonal in shape, and the average length and cross-sectional width are 209 and 175 nm respectively. The surface of the nanocrystal is smooth, defect-free, unbent, with high crystallinity and good dispersion. The electron diffraction ring corresponds to the 312, 300, and 302 crystal planes of NaYF4:Yb3+/Eu3+ micro-nano particles. NaYF4:Yb3+/Eu3+ micro-nano particles are affected by doped ions, it produces four visible lights of blue, green, yellow and red by different energy level transitions. Through fluorescence spectrum analysis of NaYF4:Yb3+/Eu3+ micro-nano particles. The asymmetry ratio of Eu3+ ion is about 1. This result shows that the magnetic dipole transition is equivalent to the electric dipole transition. Screen printing agent of NaYF4:Yb3+/Eu3+ micro-nano particles are good in different environments, the results are clear and easy to identify. However, affected by the storage environment, The results of indoor imaging have not changed much from the original imaging results. All characters of outdoor imaging are affected by moisture in the natural environment, the brightness is slightly reduced, but they can still be recognized. The imaging results show that the prepared NaYF4:Yb3+/Eu3+ micro-nano particles have the characteristics of stability and reliability in anti-counterfeiting identification, but they are still affected by natural environmental factors with a controllable degree. On the whole, it has great application prospects in anti-counterfeiting identification. ? 2021, Peking University Press. All right reserved.Accession Number: 20212010355746 -
Record 438 of
Title:Prediction of milling forces in high-speed milling optical grade SiCp/Al composites
Author(s):Guo, Lin(1); Huang, Shu-Tao(1); Yang, Hai-Cheng(2); Xu, Li-Fu(3); Zhang, Yu-Pu(3)Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering Volume: 29 Issue: 1 DOI: 10.37188/OPE.20212901.0117 Published: January 2021Abstract:Under the conditions of down and up milling, to compare the variation characteristics of milling forces of a polycrystalline-diamond single-tooth end mill with a diamond grain size of 32 μm when milling optical-grade SiCp/Al composites at high speed, the effects of the milling method and milling amounts on milling forces characteristics were studied. The empirical formulae of milling forces were also established based on a multiple linear regression analysis method. An L9(34) orthogonal cutting experiment was conducted to study the influence of milling amounts on the cutting force under the two conditions. A rotary dynamometer was then used to collect the signals of each milling force, and an empirical formula of tangential force Ft, radial force Fr, axial force Fz, and total milling force Ftotal was then established using the multiple linear regression analysis method. Experimental results demonstrated that the milling force calculated using the established regression formula was significantly high, and the average error of the model was within 10%. Under the two milling conditions, the highest level of influence on each milling force was the axial cutting depth, followed by the feed per tooth and cutting speed. To obtain smaller cutting forces, a smaller axial cutting depth should first be selected, followed by a smaller feed per tooth and a higher cutting speed. ? 2021, Science Press. All right reserved.Accession Number: 20211310138894 -
Record 439 of
Title:Accuracy-enhanced coherent Ising machine using the quantum adiabatic theorem
Author(s):Li, Lin(1,2); Liu, Hongjun(1,3); Huang, Nan(1); Wang, Zhaolu(1)Source: Optics Express Volume: 29 Issue: 12 DOI: 10.1364/OE.426476 Published: June 7, 2021Abstract:The coherent Ising machine (CIM) implemented by degenerate optical parametric oscillator (DOPO) networks is a novel optical platform to accelerate computation of hard combinatorial optimization problems. Nevertheless, with the increase of the problem size, the probability of the machine being trapped by local minima increases exponentially. According to the quantum adiabatic theorem, a physical system will remain in its instantaneous ground state if the time-dependent Hamiltonian varies slowly enough. Here, we propose a method to help the machine partially avoid getting stuck in local minima by introducing quantum adiabatic evolution to the ground-state-search process of the CIM, which we call A-CIM. Numerical simulation results demonstrate that A-CIM can obtain improved solution accuracy in solving MAXCUT problems of vertices ranging from 10 to 2000 than CIM. The proposed machine that is based on quantum adiabatic theorem is expected to solve optimization problems more correctly. ? 2021 Optical Society of America.Accession Number: 20212310450853 -
Record 440 of
Title:Magneto-optically reorientation-induced image reconstruction in bulk nematic liquid crystals
Author(s):ZHANG, YONGBIN(1,2); WANG, ZHAOLU(1); HUANG, NAN(1); LIU, HONGJUN(1,3)Source: Optics Express Volume: 29 Issue: 11 DOI: 10.1364/OE.425642 Published: May 24, 2021Abstract:We theoretically propose the magneto-optically reorientation-induced image reconstruction in bulk nematic liquid crystals (NLCs). The underlying signals are reinforced and recovered at the expense of scattering noise under reorientation-induced self-focusing nonlinearity. The intensity perturbation gain is derived and the numerical results are presented to show the response of NLC molecules to the diffusive images. The nonlinear image recovery is influenced by the input light intensity, the magnetic field direction, and the correlation length. The results suggest an alternative approach to detect noisy images and promote the application of NLCs in image processing. ? 2021 Optical Society of America.Accession Number: 20212210422607 -
Record 441 of
Title:Ultrahigh-Q terahertz sensor based on simple all-dielectric metasurface with toroidal dipole resonance
Author(s):Jiang, Xiao-Qiang(1,2); Fan, Wen-Hui(1,2,3); Chen, Xu(1); Yan, Hui(1,2)Source: Applied Physics Express Volume: 14 Issue: 10 DOI: 10.35848/1882-0786/ac27b7 Published: October 2021Abstract:A simple all-dielectric metasurface with symmetric structure, exhibiting strong toroidal dipole (TD) resonance and ultrahigh quality factor (Q-factor), is proposed. The physical mechanisms of the TD resonance are investigated by calculating the electromagnetic field and the scattering power of multipoles. Simulated results demonstrate that the Q-factor is up to 3.71 × 104 and the corresponding figure of merit is 636.7. Moreover, the TD resonance can be excited under both x- and y-polarized incident terahertz waves due to the symmetric structure. The remarkable performances make the proposed metasurface has feasible capability for biological and chemical sensing in terahertz range. ? 2021 The Japan Society of Applied Physics.Accession Number: 20214111016451 -
Record 442 of
Title:Terahertz photoconductive antenna based on antireflection dielectric metasurfaces with embedded plasmonic nanodisks
Author(s):Jiang, Xiao-Qiang(1,2); Fan, Wen-Hui(1,2,3); Song, Chao(1); Chen, Xu(1); Wu, Qi(1,2)Source: Applied Optics Volume: 60 Issue: 26 DOI: 10.1364/AO.431678 Published: September 10, 2021Abstract:By taking advantage of dielectric metasurfaces and plasmonic nanostructures, a terahertz photoconductive antenna (THz-PCA) is proposed and investigated in detail. The designed dielectric metasurfaces can reduce the optical reflection down to 1.4% and accelerate the switching process (electric conductive to resistive) that broadens the THz spectrum emitted from THz-PCA. Simultaneously, the embedded plasmonic nanostructures can realize 11.2 times enhancement in local electric field without affecting the switching process and the damage threshold of the THz-PCA. Simulated results indicate that the proposed THz-PCA is 70.56 times stronger in THz radiation power than that of the traditional THz-PCA. The significant enhancement ensures the proposed THz-PCA has great prospects in promoting THz technology based on the THz-PCA. ? 2021 Optical Society of AmericaAccession Number: 20213610874252 -
Record 443 of
Title:Enhanced optical absorption surface of titanium fabricated by a femtosecond laser assisted with airflow pressure
Author(s):Li, Xun(1,3); Li, Ming(1); Liu, Hongjun(1,2)Source: Chinese Optics Letters Volume: 19 Issue: 9 DOI: 10.3788/COL202119.091404 Published: September 2021Abstract:We propose an effective way to achieve an enhanced optical absorption surface of titanium alloy 7 (Ti7) fabricated by a femtosecond (fs) laser assisted with airflow pressure. The effect of laser scanning speed and laser power on the surfaces' morphology and average reflectivity was studied. In order to further reduce the surface's reflectivity, different airflow pressure was introduced during the fabrication of Ti7 by a fs laser. Furthermore, the average reflectivity of samples fabricated under different laser parameters assisted with airflow was presented. In addition, the high and low temperature tests of all samples were performed to test the stability performance of the hybrid micro/nanostructures in extreme environments. It is demonstrated that the airflow pressure has an important influence on the micro/nanostructures for light trapping, the average reflectivity of which could be as low as 2.31% over a broad band of 250-2300 nm before high and low temperature tests, and the reflection for specific wavelengths can go below 1.5%. ? 2021 OSA - The Optical Society. All rights reserved.Accession Number: 20212410479921 -
Record 444 of
Title:Advances in G-stack diode laser using macro-channel water cooling and high thermal conductivity material packaging
Author(s):Han, Yang(1); Sun, Lichen(1); Fu, Tuanwei(1); Gao, Lijun(1); Zheng, Yanfang(1); Chen, Yunzhu(1); Zhang, Xiaojuan(1); Yan, Minna(1); Zhao, Sicheng(1); Yang, Kai(1); Gao, Lei(1); Zah, Chungen(1); Liu, Xingsheng(1,2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11668 Issue: DOI: 10.1117/12.2582695 Published: 2021Abstract:There are strong demands at the market to increase power and reliability for high power diode laser. In parallel to this the requirements for cooler and package for the high power diode laser increase. Superior heat dissipation capability and low thermal resistance are some of the key attributes for the diode laser package design in the near future. The most common method of removing the large amounts of waste heat in a diode laser is using a micro-channel cooler. However, a microchannel cooler requires water to meet demanding specifications to avoid failures due to corrosion, which increases the overall cost to operate and maintain the laser. We demonstrate advances in a new macro-channel water cooling diode laser which are designed to eliminate the failure mechanisms associated with micro-channel coolers, and enhance the laser heat dissipation and the long-term reliability. For the package adopting the high thermal conductivity material, the maximum output power is 100 W per bar in CW mode. Due to the advantage of compact design, high power, high reliability and fast axis collimation, the new diode laser has the potential to be widely used in many fields, such as pumping solid state laser, hair removal, industry and research. ? 2021 SPIE. ? 2021 SPIE. All rights reserved.Accession Number: 20212510525586