激光二极管抽运(Tm,Ho)∶YLF激光器光谱特性实验分析

Ho∶YLF晶体的5I7和5I8斯塔克能级分裂数较多,形成2047~2070nm宽的增益谱带,对于可调谐2μm激光及宽带激光放大器研究具有重要意义。理论上分析了(Tm,Ho)∶YLF晶体的能级结构,并对晶体掺杂浓度和长度进行了优化。实验研究了激光二极管抽运微片Tm(原子数分数0.06),Ho(原子数分数0.004)∶YLF激光谱线可调谐特性,调谐范围2.0656~2.0671μm。利用(Tm,Ho)∶YLF晶体的宽增益谱特性,将其作为激光二极管抽运激光放大器,成功地将2.048μm(Tm,Ho)∶GdVO4激光功率放大了2.5倍。实验上测量了(Tm,Ho)∶YLF晶体在强抽运条件下480~492nm及530~550nm可见波段的上转换蓝绿光荧光谱。     

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。     

全光学高灵敏度铷原子磁力仪的研究

报道了一种全光学的高灵敏度铷原子磁力仪.其原理是基于激光束与处于微弱磁场中的铷原子的相互作用.这种相互作用与铷原子所处的环境中的磁场有关,因而通过测量透过铷原子气体的激光强度的变化可以获得磁场信息.分析了该磁力仪的工作原理,建立了相应的实验装置,并对其性能进行了测试.结果表明实验结果与理论相符合.进一步研究了影响磁力仪灵敏度的一些因素,提出了优化各参数来提高磁力仪灵敏度的方法.     

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.     

Influence of Fano interference and incoherent processes on optical bistability in a four-level quantum dot nanostructure

Role of Fano interference and incoherent pumping field on optical bistability in a four-level designed In Ga N/Ga N quantum dot nanostructure embedded in a unidirectional ring cavity are analyzed. It is found that intensity threshold of optical bistability can be manipulated by Fano interference. It is shown that incoherent pumping fields make the threshold of optical bistability behave differently by Fano interference. Moreover, in the presence of Fano interference the medium becomes phase-dependent. Therefore, the relative phase of applied fields can affect the behaviors of optical bistability and intensity threshold can be controlled easily.     

循环跃迁的Δ 型三能级系统中的无反转激光

研究了在引入非相干抽运的情况下,循环跃迁的Δ型共振三能级系统中产生的无反转激光.利用主方程的方法, 导出了缀饰态中强相干场极限下布居数项和相干项的稳态近似解析解以及产生无反转激光所需要满足的条件;并利用数值模拟的方法讨论了布居数分布、 系统增益对探测场和相干场拉比频率的依赖性以及随时间的演化规律. 结果表明:无论各个参量取何值,共振Δ型三能级系统总是处于无粒子数反转的状态; 只要探测场或相干场之中有一个为强场,便可产生无反转激光; 当其中任意一个场远强于另一个场时,系统的无反转增益将不再依赖于任何一个场的拉比频率.     

光磁共振实验中扫场及水平场取值关系的探讨

在光磁共振实验中,常常有抽运信号与共振信号同时存在的情况,这严重影响到实验的观察和测量.本文利用扫场及水平场大小对抽运信号的影响,通过理论分析和实验测量得到抽运和共振信号不同时存在时扫场和水平场的取值关系.从而有效避免抽运信号对共振信号的干扰,以及对总磁场方向误判的情况,保证了实验的顺利进行和准确测量.     

1064nm纳秒激光脉冲激发的外腔式PbWO4拉曼激光器

研究了外腔式PbWO4拉曼激光器在纳秒脉冲抽运下的输出特性。利用主动调Q的Nd:YAG激光器产生的脉冲宽度为31.4ns,最大输出能量为200mJ的1064nm激光作为抽运源。拉曼激光谐振腔采用的是平凹腔设计。测量了输出的拉曼光脉宽与抽运能量的关系,分析了输出的拉曼光脉冲波形图和光谱图,测量了输出的拉曼光脉冲能量与抽运能量的关系,计算了转换效率与抽运能量的关系。当注入抽运光能量达到42mJ时,得到了一阶斯托克斯光脉冲的最大能量和转换效率分别为10mJ和24%,获得外腔式PbWO4拉曼激光器的一阶斯托克斯光脉冲波长为1177.6nm,典型的一阶斯托克斯光脉冲脉宽为20ns。     

Orientational Recognition and Low-Resistance Passing (LRP) Regulation of Segmental Re-innervation by Central Neurons in Leeches

Re-innervation of sensory and motor neurons on a defined area of the body wall was studied in two species of leeches, Whitmania pigra and Hirudo medicinalis, as a model of segmental animals. Following isolation and rotation of a tube of body wall, the mechanical sensory and annular erection (AE) motor neurons re-innervated the body wall, at a rate of approximately 3. 8 -8. 4 μm/h. The patterns of re-innerva-tion by pairs of neurons on each side of a ganglion were bilaterally symmetric. The repairs are synchronous for the sensory and motor neurons which are of different functions but in a same ganglion. The gap junctions are widely spread in leech between neurons and glia cells, as well as among the neurons and glia cells themselves. Therefore, it is proposed that the nervous system repair is regulated by a low-resistance pathway. In the xenotransplantation experiments, neurons recognized target tissues before the immuno-recognition and rejection.     

肌红蛋白的同步荧光光谱

首次对肌红蛋白的同步荧光光谱进行了研究,并对肌红蛋白荧光峰予以归属。当△λ为20nm时,308nm处的荧光峰主要为酪氨酸残基的贡献,很小一部分是由色氨酸残基贡献的;△λ为40nm时,分别在322和596nm处观察到两个荧光峰,322nm的荧光峰为酪氨酸和色氨酸残基的共同贡献,596nm的荧光峰则归属为肌红蛋白分子中血红素的贡献。