LD抽运Cr,Tm,Ho∶YAG微片激光器单纵模运转特性的研究

研究了LD抽运的单纵模Cr,Tm,Ho∶YAG微片激光器,激光器厚度为1?mm,在用波长785?nm的LD进行端面抽运时,激光器阈值为1060?mW,单纵模激光最大输出功率为31?mW. 对激光器输出功率随温度变化特性进行了研究,验证了CTH∶YAG晶体的温度敏感性. 还研究了激光器的温度调谐特性,实验测得激光器的温度调谐系数为14?GHz/℃. 关键词： 激光光学 CTH∶YAG微片激光器 LD抽运 单纵模运转     

High repetition rate laser pulses amplified by Nd/Cr:YAG ceramic amplifier under CW arc-lamp-light pumping

Laser pulses with high repetitive rate generated from a Q-switch microchip Nd:YAG oscillator were amplified by Active mirror composed of Nd/Cr:YAG ceramic pumped by CW arc-lamp. The laser pulses were amplified, and saturation of averaged output laser power was observed. Repetitive ratio of injected laser pulses was changed from 20 to 100 kHz. Averaged output laser power and gain were measured, and gain coefficient and power-extraction efficiency were evaluated. Output laser power was calculated and compared to experimentally measured one, and the calculated results are consistent with the experimental ones. For amplification of laser pulses with high repetitive ratio, this laser material can realize very high laser gain with low pumping power density and high optical-optical conversion efficiency under CW-lamp-light pumping.     

光泵磁共振实验探究

本文分析了光磁共振实验中,观察到光抽运信号和磁共振信号的条件,并重点对方波和三角波扫场对光抽运信号和磁共振信号的作用和影响进行了讨论,阐明了应如何选择方波和三角波扫场信号的大小和方向,才能得到理想的光抽运信号和磁共振信号。     

Rb87基态超精细塞曼能级跃迁的偏振激发特性

本论述了Rb^87基态超精细塞曼能级光泵磁共振的偏振激发特性,给出了塞曼能级跃迁谱线随抽运光偏振特性的变化。     

A standing wave model for acoustic pumping effect in microchannels

An acoustic impedance pump is comprised of a compressible section coupled at both ends to sections of different acoustic impedances. Liquid can be pumped from one end to another if the compressible section is actuated at certain locations. This paper presents an analytical model on the acoustic pumping effect in microchannels. A one-dimensional wave equation is developed for acoustic pressures in the compressible section, taking into account the actuations as acoustic source terms. The solution for the acoustic pressure is a set of standing waves established inside the compressible section, corresponding to the actuations. The pumping effect is attributed to the second-order terms of the acoustic pressures. Two control parameters are identified. One is the resonance frequency associated with the sound wave speed and length of the compressible section, and the other is the damping factor. The analytical results are compared with the experimental data, and a qualitative agreement is observed in terms of frequency characteristics of the pumping pressure.     

Air-related mechanisms of noise generation by solid rubber tyres with cavities

There are four main air-related noise generation mechanisms at the tyre/road interface, which were all categorised more than 20 years ago. The first one is the so-called ‘air pumping’ mechanism. Two other air-related phenomena that occur when there are air movements near the contact patch of the tyre are ‘air resonant radiation’ and ‘pipe resonances’ which appear at the footprint of the tyre. In addition to these, there is a forth effect, which is mentioned in the literature, that is occurring due to turbulence effects of the air surrounding the spinning tyre. There has been less focus on the air-related mechanisms than on other types of tyre noise generation mechanisms. This paper attempts to add some detail to current understanding of the air-related noise generation at the tyre road interface and gives some further information on how to identify the differences due to these mechanisms. Specifically in the present paper, a solid rubber tyre running on a vehicle chassis dynamometer is used to study the first two mechanisms. This is done with emphasis on the time history of the recorded signal and not on the frequency spectrum, as is more commonly used. A comparison with existing theoretical models of these mechanisms reveals some of the strength and weaknesses of the current understanding of these phenomena.     

Thermo-Magneto-Electric Currents with Dynamical Magnetization Inhomogeneities

We study the effect of potential and thermal gradient induced non-equilibrium magnetization in quasi 1-d itinerant magnets. A semi-phenomenological theory is employed in conjunction with the drift-diffusion model for this study. Using the methods of non-equilibrium thermodynamics, we derive the transport currents corresponding to charge, heat, and magnetization flows in the presence of non-equilibrium magnetization textures.It is shown how time-dependent magnetic textures give rise to charge and thermalcurrents even in the absence of external potential and thermal gradients through spinpumping.The presence of dynamical textures also affect the thermodynamic parameters of the system. As an application, we consider the case of a helimagnet.     

An alytical and numerical study of peristaltic transport of a Johnson-Segalman fluid in an endoscope

In the present study, we discuss the peristaltic flow of a Johnson-Segalman fluid in an endoscope. Perturbation, homotopy, and numerical solutions are found for the non-linear differential equation. The comparative study is also made to check the validity of the solutions. The expressions for pressure rise frictional forces, pressure gradient, and stream lines are presented to interpret the behavior of various physical quantities of the Johnson-Segalman fluid.     

不同排布方向性椭圆孔液体润滑机械密封性能的研究

为提高液体润滑多孔端面密封的动压性能,提出了方向性多孔端面机械密封.考虑端面间润滑液膜的空化现象,基于质量守恒的JFO空化边界条件建立了理论模型,采用有限差分法求解Reynolds控制方程,获得了端面膜压分布,从而对比分析了方向性椭圆孔的排布方式对多孔端面机械密封性能的影响规律.结果表明:椭圆孔的方向性排布对端面密封的密封性能影响较大,高压侧下游泵送孔可有效提升密封端面的流体动压特性,上游泵送孔不论在高压侧还是在低压侧均可有效降低密封泄漏率;当形状因子γ为3~5,内外孔倾斜角α为35°~45°和β为125°~135°时,可获得最佳的动压性能,当形状因子γ为3~5,倾斜角α为30°~50°和β为30°~50°时,可以获得最低泄漏率.     

Influence of pumping laser bandwidth on the quantum fluctuation chracteristic of non-degenerate optical parametric amplifier

Usually the quantum fluctuation characteristic of the non-degenerate optical parametric amplifier is analysed under the assumption of monochromatic pumping. However, in experiments, the driving beam with finite bandwidth is used to obtain the non-degenerate signal and idler beam amplifications. On account of that, we derive an analytical solution for the non-degenerate optical parametric amplification system with finite bandwidth laser pumping, and evaluate the associated quantum fluctuation. Finally, the application of the V₁ criterion to the bipartite entanglement is discussed.