半导体微腔激光器瞬态特性的分析

建立了反映半导体微腔激光器特性的模型,借助计算机手段,运用Matlab软件直接给出了半导体微腔激光器瞬态响应的仿真结果及载流子密度和光子密度的相图,分析了自发辐射因子、注入电流和腔长对微腔器的激射阈值、延迟时间、驰豫振荡频率和光输出等参量的影响。该模型及有关结合为半导体微胶激光器的工艺制作,改善的高频调制特性和优化器件提供了理论依据。     

一个关于铷原子频标新方案的建议

本文提出一种在~(87)Rb气泡式原子频标中消除碰撞频移、光频移和微波功率频移的新方案,有可能大大提高它的性能。     

PBR-MⅡ型~87Rb激射器的改进及短期频率稳定度测量

介绍了PBR-MⅡ型铷激射器物理部分及电路系统的改进;测量了改进后激射器的输出功率及短期频率稳定度,其结果有明显提高,并对结果进行了拟合、分析,其噪声特性与理论相符。     

KNSBN晶体鸟翼式互抽运相位共轭器的研究

利用我国山东大学研制的KNSBN晶体实现鸟翼式互抽运相位共轭器(BWPC),实验研究互抽运相位共轭反射率随互抽运光束的入射角度,入射位置,入射光抽运比的变化而变化的规律。     

基于分子蒸馏原理的高纯铯制备研究

为了进一步提高原子钟用金属铯的纯度,以99.5%的精铯为原料,采用分子蒸馏的方法提纯金属铯。通过实验研究了蒸馏温度、刮膜器转速、进料速率对金属铯提纯效果的影响,得到最佳的实验条件如下:蒸馏温度控制在490~510 K之间,刮膜器转速设定在180~210 r/min之间,进料速率在3~5 g/min之间。在上述条件下进行实验,结果表明:蒸馏产品中所有的杂质含量均有显著下降,其中钾(K)的含量从690×10~(-6)下降至10~6×10~(-6),铷(Rb)的含量从840×10~(-6)下降至123×10~(-6),该方法能够制得纯度为99.95%的高纯金属铯,满足了铯原子钟对金属铯原料的要求。此外,与普通的真空蒸馏相比,分子蒸馏的蒸馏温度更低,蒸馏时间更短。     

使用Fabry—Perot干涉腔稳频的GaAlAs激光器(英文)

GaAlAs激光器的激射频率被锁定于Fabry-Perot干涉腔上。在锁定之后其激射频率的涨落已被大大地降低。所测得的频率稳定度(对Fabry-Perot干涉腔中心频率的跟踪稳定度)如下:其中第1个稳频系统为5×10~(-12)(1s)、1.5×10~(-12)(10s)、1.2×10~(-12)(100s);而第2个稳频系统为8×10~(-12)(1s)、2×10~(-12)(10s)、1.8×10~(-12)(100s)。     

光纤光栅半导体激光器激射波长与Bragg波长的偏离

利用包含光纤布拉格光栅(FBG)反射率分布的光纤光栅外腔半导体激光器(FGSL)的理 论模型,对FGSL 的激射波长进行了研究。结果表明激射波长并不一定在FBG布拉格反射波长处;布拉格反射波长相对于激射波长的偏移量与FBG的反射率分布、半导体增益介质的增益谱分布及增益峰值波长有关;激射波长可大于或小于布拉格反射波长。     

模拟核芯FCM燃料的振荡烧结行为研究

全陶瓷微封装弥散(FCM)燃料以其较好的固有安全性而成为核能领域研究的重点。针对SiC基体难以烧结的问题,本研究利用振荡烧结具有加速传质和降低烧结温度的优势,开展了模拟核芯FCM燃料振荡烧结行为研究,重点考察了振荡烧结温度、振荡时间与振荡压力等参数对基体致密化行为的影响,并与热压烧结结果进行了对比。结果表明,振荡烧结温度、保温时间以及中值压力对基体致密化有重要影响,而振荡压力的振幅对基体致密化影响不大。相比于热压烧结,振荡烧结可以提高材料的致密度,振荡烧结试样的致密度更高, 1850℃振荡烧结试样的致密度为99.99%;振荡烧结试样的晶粒尺寸更小,1850℃振荡烧结试样的晶粒尺寸为(284±4)nm,比同等温度下热压烧结试样的晶粒尺寸减小～27%;振荡烧结试样的硬度更高, 1850℃振荡烧结试样的硬度为(26.7±0.4) GPa。借助改进的热压烧结本构方程,计算得到试样在致密度为90%时的应力指数n=1,活化能Q=430 kJ/mol,致密化的主导机制为晶界扩散协调的晶界滑移。     

超薄铋薄膜的量子尺寸效应

采用基于密度泛函理论的第一性原理方法,研究了2～16层Bi(111)薄膜的表面能和功函数,它们展现出量子尺寸效应引起的奇偶振荡.解释这种振荡需要考虑表面投影能带结构,振荡周期与量子阱态在二维布里渊区中高对称点费米能级处的穿越有关,量子阱态穿越费米能级亦引起态密度在费米能级处振荡,预示传导性质的振荡转变.     

利用慢波结构的小型化铷原子频标

作者等前曾撰文叙述了一种螺旋线微波慢波结构,在气泡式铷原子频标中用它代替传统的微波谐振腔,既可以大大减小泵体体积,又可获得较高的~(87)Rb原子基态0-0跃迁谱线的信噪比。本文将报导利用这种慢波结构的铷原子频标泵体的性能和存在问题,以及用这样的泵体做成的小型化铷原子频标的整机性能。     

Oscillation characteristics analysis of transversely and coaxially pumped Ti-diffused Nd:MgO:LiNbO3 waveguide lasers

Abstract

A theoretical analysis of oscillation characteristics is developed for Ti-diffused Nd:MgO:LiNbO₃ waveguide lasers by using the formalism of mode overlap. Simple and explicit expressions in terms of mode sizes are derived for effective mode volume and coupling efficiency between pump mode and laser mode, which are directly proportional to the threshold pump power and slope efficiency, respectively, both for transverse and coaxial pumping considering the spatial distribution of the pump beam and the laser beam. A comparison for the two pumping configuration has shown that the transverse pumping requires much higher input pump power and has much lower slope efficiency than the coaxial pumping. The fundamental transverse mode (TM ₀) oscillation conditions relative to the cavity loss are also discussed for the two pumping configurations.

Indexing terms: Ti-diffused Nd:MgO:LiNbO ₃ waveguide laser, effective mode volume and coupling efficiency, threshold pump power and slope efficiency, transverse and coaxial pumping, single mode oscillation condition.     

Periodic pulse oscillation in an intracavity-doubled Nd:YVO(4) laser

We report periodic pulse oscillation in an intracavity-doubled Nd:YVO(4) laser. The pulse oscillation is caused by alternate oscillation between two modes. We investigated improvement of green-light power with the pulse oscillation in a Nd:YVO(4) laser. The pulse oscillation gave a factor of approximately 2 higher average green-light power than that for cw oscillation at the same pumping power.     

Excitation of a Cr:forsterite laser to the (3)T(1) band

Laser oscillation of Cr:forsterite was obtained with ruby laser pumping to the lowest-lying levels of the (3)T(1) band in Cr(4+). Pump polarization effects, temporal response, and broadband 220-nm tuning are reported. Frequency doubling in potassium titanyl phosphate generate tunable red-yellow light. This unconventional excitation scheme is of interest for potential high-energy output and for direct diode pumping.     

Control of giant pulse duration in neodymium minilasers with controllable cavity length and pulsed pumping

In a solid-state laser incident on a LiNdP4O12 crystal, pumped by a short light pulse, giant pulse oscillation without the use of resonator Q switching is realized. Tuning of the oscillation pulse duration from 2 up to 20 ns is achieved by changing the cavity length from 24 to 3 mm, respectively. Our analysis of this mode of laser radiation is made on the basis of the rate equations. The factors influencing oscillation pulse duration are investigated. It is shown that in a limiting case the minimal value of the pulse duration is limited by only the rate of excitation transfer from the pumping band to the metastable level.     

Investigation of Cr:Tm:Er:YAG laser crystals in a resonator with various degrees of spectral selectivity

It has been established that Tm(3+) ions do not prevent multiple-wavelength oscillation in Cr:Tm:Er:YAG laser crystals inserted inside of the completely nonselective mirror resonator. The output mirror spectral selectivity needed for single-wavelength oscillation at 2.697 mum for a considerable excess of pumping energy over the threshold has been determined experimentally. It has been shown that Tm(3+) optimum concentration in the crystals could be determined correctly in the described resonator scheme.     

Effects of design inhomogeneities of the dynamic response of a spherical shell

An experimental study has been done on how the rigidity and menial parameters of design inhomogeneities affect the dynamic deformation in a spherical shell on account of an explosion at the center in a spherical charge of condensed explosive. The dynamic response in particular includes a cyclic increase in the oscillation amplitude (pumping effect), but it is substantially dependent on the size and mass of the design inhomogeneities. Assumptions made by others on the pumping mechanisms in theoretical studies are confirmed.Translated from Problemy Prochnosti, No. 1, pp. 89–96, January, 1993.     

Thermoacoustic effects of inviscid fluids

Thermoacoustic effects of inviscid fluids are studied with the use of linearized hydrodynamic equations. The heat flux and the acoustic energy source due to acoustic waves are related to entropy oscillations due to irreversible processes, and are evaluated for a plane wave in a long cylindrical tube with the boundary condition that the local oscillation of the temperature is absent at the wall surface. The heat flux and acoustic energy source obtained in the standing wave approximation give qualitative explanations of heat pumping and similar experiments and stability limits.     

Efficient energy transfer between Ce/Cr and Nd ions in transparent Nd/Ce/Cr:YAG ceramics

This paper reports the spectroscopic and laser characteristics of transparent ceramics of YAG:Nd co-doped with Ce and Cr. The ceramics were prepared by advanced ceramic techniques and showed more than 85% of transparency. Diode pumped laser oscillation performed at different output coupler transmissions (T) showed that a maximum slope efficiency of 16% was achieved for T = 3%. The cross energy transfer mechanism under violet laser diode pumping has been analyzed and the possible energy transfer mechanisms have been proposed using the various energy levels of the dopant ions. The emission lifetimes of the dopant ions at two different concentrations have also been found.     

InAsSb/InAsSbP heterostructure lasers with a large range of current tuning of the lasing frequency

The lasing spectra and the shift in the position of the modes in the current range (1–5)I _th with various methods of pumping the nonequilibrium charge carriers are analyzed. It is shown that the pumping method does not influence the character of the tuning of the radiation line. The large short-wavelength tuning range (up to 50 Å) is due not to the heating of the crystal lattice in the active-region material but rather the nonuniform nonequilibrium charge-carrier density distribution over the width of the stripe. Pis’ma Zh. Tekh. Fiz. 25, 17–23 (October 12, 1999)     

Parametric regeneration of spin oscillations of a thin-film ferromagnetic cavity by microwave pumping

An experimental investigation is made of the regeneration of spin oscillation losses in a thin-film ferromagnetic cavity by parametric pumping. It is observed that effective regeneration only takes place in narrow frequency intervals in zones of strong dispersion near dipole gaps in the spin wave spectrum of thin films with bounded mobility of the surface spins. It is shown that microwave parametric pumping can substantially improve the Q factor of dipole-exchange spin oscillations of the thin-film cavity. Pis’ma Zh. Tekh. Fiz. 23, 82–87 (August 26, 1997)