Laser performance of monolithic Cr,Nd:YAG self-Q-switched laser

The self-Q-switched laser performance of monolithic Cr⁴⁺,Nd³⁺:YAG concave-planar resonator with 5-mm length was studied experimentally and theoretically. The slope efficiency is as high as 24% and pump threshold is as low as 64 mW. The pulse width, the single pulse energy and the pulse repetition rate of monolithic Cr,Nd:YAG self-Q-switched laser were measured as a function of absorbed pump power. With the increase of pump power, the pulse width decreases and the pulse energy and the pulse repetition rate increase. The average output power of 91 mW with pulse width of 7 ns at repletion rate of 35.5 kHz was obtained at the maximum absorbed pump power of 440 mW, the peak power is as high as 370 W. The theoretical prediction of pulse energy, pulse width and pulse repetition rate as a function of absorbed pump power based on rate equations is in a good agreement with our experimental data. This can lead to develop the diode laser-pumped monolithic self-Q-switched solid-state microchip lasers.     

平板型太阳热水器板芯高温耐久性实验方法研究

为了研究平板型太阳热水器板芯表面的高温耐久性,结合国外的实验方法及国内的应用特点设计了本实验方法.该方法以板芯表面光学性能的衰减来推断系统的寿命,即在一定的高温实验条件下模拟加速衰减过程,以板芯表面光学性能衰减小于5%作为判断板芯合格标准.     

考虑振源阻抗影响的动力吸振器优化设计

本文从四端参数技术入手,着重研究振源特性对动力吸振器优化设计的影响,进行了理论推证。且与传统优化设计进行比较,最后通过回转惯性振源的计算,进行了讨论.     

Crack-free micromachining on glass substrates by visible LIBWE using liquid metallic absorbers

Laser induced backside wet etching (LIBWE) is a promising laser direct-write technique for etching transparent materials and for producing high precision and near-optical quality surfaces. In this study, visible LIBWE using gallium and eutectic indium/gallium as absorbers was used for crack-free microfabrication of sodalime and quartz. Eutectic indium/gallium (In/Ga) has a melting temperature lower than metallic gallium does and the etching rate by using In/Ga was found to be similar to that by gallium for visible LIBWE. When using the gallium absorber, the etching threshold of quartz by visible LIBWE was about one-third of that by UV LIBWE. The heat-affected zone of the quartz etching was negligible at the trench rim in the visible LIBWE process. The wettability of the metallic absorbers on the substrates affects aspect ratio and is a new important factor for LIBWE. In addition, etching rate decreased when repetition rate was increased.     

基于宽边耦合螺旋结构的低频小型化极化不敏感超材料吸波体

设计、仿真并实验验证了基于宽边耦合螺旋结构的低频小型化超材料吸波体. 实验测试结果表明, 该超材料吸波体在1.39 GHz吸收率达到最大为98%, 其单元尺寸和总厚度均为6.8 mm, 约为1/32工作波长, 实现小型化窄带吸波. 由于吸波体中螺旋结构是旋转对称排列的, 因而其对垂直入射电磁波的极化方向是不敏感的. 此外, 该超材料吸波体对斜入射横电和横磁极化电磁波在60°时, 仍具有强吸收. 关键词： 超材料 吸波体 小型化     

Band gap tunable and improved microstructure characteristics of Cu2ZnSn(S1−x,Sex)4 thin films by annealing under atmosphere containing S and Se

Cu₂ZnSn(S_xS_1?x)₄ (CZTSSe) thin films were prepared by annealing a stacked precursor prepared on Mo coated glass substrates by the sputtering technique. The stacked precursor thin films were prepared from Cu, SnS₂, and ZnS targets at room temperature with stacking orders of Cu/SnS₂/ZnS. The stacked precursor thin films were annealed using a tubular two zone furnace system under a mixed N₂ (95%) + H₂S (5%) + Se vaporization atmosphere at 580 °C for 2 h. The effects of different Se vaporization temperature from 250 °C to 500 °C on the structural, morphological, chemical, and optical properties of the CZTSSe thin films were investigated. X-ray diffraction patterns, Raman spectroscopy, and X-ray photoelectron spectroscopy results showed that the annealed thin films had a single kesterite crystal structure without a secondary phase. The 2θ angle position for the peaks from the (112) plane in the annealed thin films decreased with increasing Se vaporization temperature. Energy dispersive X-ray results showed that the presence of Se in annealed thin films increased from 0 at% to 42.7 at% with increasing Se vaporization temperatures. UV–VIS spectroscopy results showed that the absorption coefficient of all the annealed thin films was over 10⁴ cm^?1 and that the optical band gap energy decreased from 1.5 eV to 1.05 eV with increasing Se vaporization temperature.     

混沌的抑制研究进展综述

综述了抑制混沌的４种主要方法:加随机噪声、加周期摄动、加动力吸振器和加输出变量反馈．概括了各种方法的一般形式,列举了各种方法应用的例子,还指出一些尚待研究的问题．      

Mathematical modeling of TE CO2 laser with SF6 as a saturable absorber

A mathematical model describing the dynamic emission of a single mode TE CO₂ laser with saturable absorber has been adapted. A six-temperature model has been used to describe the amplifying medium, while a four-coupled energy level is used to describe the selective absorbing medium. The suggested mathematical model allows the investigation of the effects of the intracavity absorber on the mode characteristics of the TE CO₂ laser and, moreover, the study of the effect of the laser input parameters on the output laser pulse. The model simulates the passive Q-switch in both low- and high-pressure cases in the absorbing medium.

In addition, numerical solutions of a non-linear rate equation system of the suggested model are quantitatively discussed. The solutions describe the photon number density, the population inversion and the energy transfer processes of amplifying and absorbing media.     

Multiple-valued steady states and their stability in a saturable-absorber laser

We present the results of a theoretical consideration of steady states in a saturable-absorber laser for different frequencies of transition in the active medium, the absorber, and the cavity. The conditions for the coexistence of several (up to five) stationary values of intensity are obtained. The stability of such states is analytically studied, and the possible regimes of generation and switching for the parameters corresponding to solid-state lasers with a saturable absorber are shown. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 322–326, May–June, 2000.     

基于声学超材料的低频可调吸收器

在当今社会,噪声污染已经成为人类健康的一大威胁,如何有效地控制和消除噪声污染一直是科研领域的一个重要话题.本文以开口环嵌套结构为模型,设计并制备了一种声学超材料.通过理论分析、数值模拟和实验测试,发现由于模型内部空腔的强烈耦合共振效应,该超材料可以在低频区域实现接近完美的吸声效应.此外,通过简单地绕轴旋转其内腔开口方向,即可改变该超材料的相对阻抗值,进而在较宽的频带范围内实现对吸收峰位置的可调控制.由于该超材料具有深亚波长的尺寸,因此非常有利于低频吸声器件的小型化和集成化,同时该模型也为宽带吸收器的设计奠定了基础.