Well-width dependence of the phase coherent photorefractive effect in ZnSe quantum wells

We report on the well-width dependence of the phase coherent photorefractive (PCP) effect in ZnSe/ZnMgSe single quantum wells (QWs) using 90 fs light pulses. The experiments are performed in a four-wave-mixing configuration at temperatures between 25 and 65 K. The ZnMgSe/ZnSe QWs with 10, 5 and 3 nm well width were grown on GaAs substrate using molecular beam epitaxy. With decreasing QW thickness we observe a reduction of the PCP diffraction efficiency. This is attributed to the higher electron energy in small QWs due to the quantum size effect, which leads to a reduced equilibrium density of captured electrons in the QW. With increasing temperature the PCP signal further decreases which is attributed to thermal activation of the QW electrons back to the GaAs substrate.     

受驱动的关联发射激光:双模亚泊松光

如果在关联发射的基础之上再引入原子相干，这样的系统可产生明亮的双模亚泊松光。运用Ｓｃｕｌｙ－Ｌａｍｂ理论计算ＭａｎｄｅｌＱ因子，一方面，当相对相位和相对振幅的量子噪声被抑制到真空噪声水平时，平均模呈现亚泊松光子分布；或者当平均相位和平均振幅的量子噪声被抑制到真空噪声水平时，相对模呈现亚泊松光子分布，ＭａｎｄｅｌＱ因子的最佳值均可达到－０．５。在上述两种情况下，每个关联发射激光（ＣＥＬ）模呈现亚泊松光子分布，ＭａｎｄｅｌＱ因子的最佳值均可达到－０．２５。     

氦氖激光纵模脉冲检测及其数据处理

在分析常用低噪声快速光电探测器的基础上,选择PIN光电二极管来探测氦氖激光纵模脉冲。通过合理设计降低前放电路的噪声,根据被测脉冲频率设计探测电路的带宽,达到提高信噪比的目的。同时在后端的数据处理中,根据激光脉冲的波形函数,利用曲线拟合的方法来进一步去除测量中的各种噪声,从而准确地了解脉冲的形状、相位等信息,大大地提高了在现有硬件设备条件下测量的准确性,减小了测量误差。     

三硼酸锂晶体的多光子散射

本文报道三硼酸锂(LBO)晶体的瞬态前向相干多光子散射,实验表明LBO晶体内部同时发生x~(2)和x~(3)非线性相互作用过程,而未发现光耦合效应,测量了LBO晶体的光栅寿命上限.     

光源编码的白光散斑剪切干涉计量术

本文提出了一种用非相干光源照明进行剪切干涉计量的方法—光源编码的白光散斑剪切干涉计量术.它采用光栅对光源进行编码以提高空间相干性,使物体的两个剪切像的波面部分相干叠加,以实现剪切干涉.     

基于一种电流控制型芯片的开关电源

阐述了电流控制型开关电源的基本原理，并将其与电压控制型开关电源进行了比较，指出了电流型控制的优点，并介绍了一种常用的电流型控制芯片（TOPswitch-Ⅱ）及基于该芯片的开关电源。     

Λ型原子与单模光场的非共振作用制备四光子相干态

根据简并Λ型三能级原子与单模光场的改进型有效哈密顿量 ,通过矩阵形式法推导出原子光场系统的波函数 ,提出利用简并Λ型三能级原子与单模光场的远离共振相互作用制备四光子相干态的有效方案。并且证明按照同样的方法不能制备出四成分以上的相干叠加态 ,即当在腔中注入的第三个原子的速度与第二个原子的速度相等时 ,腔场将保持这种四光子相干叠加态不变     

Coherent states of general time-dependent harmonic oscillator

By introducing an invariant operator, we obtain exact wave functions for a general time-dependent quadratic harmonic oscillator. The coherent states, both inx- andp-spaces, are calculated. We confirm that the uncertainty product in coherent state is always larger thankh/2 and is equal to the minimum of the uncertainty product of the number states. The displaced wave packet for Caldirola-Kanai oscillator in coherent state oscillates back and forth with time about the center as for a classical oscillator. The amplitude of oscillation with no driving force decreases due to the dissipation in the system. However, the oscillation with resonant frequency oscillates with a large amplitude, even after a sufficient time elapse.     

Covariance of the grassmann star product

Using the coherent states of many fermionic degrees of freedom labelled by Grassmann variables, we introduce the noncommutative (precisely non-anticommutative) Grassmann star product. The covariance of this star product under unitary transformations, particularly the canonical ones, is studied. The super star product, based on supercoherent states of supersymmetric harmonic oscillator, is also considered.     

HIGH RESOLUTION SPECTROSCOPIC STUDY OF THE LOCAL MODE VIBRATIONAL STATES OF SILANE

The stretching vibrational overtone bands (3000), (4000) and (5000) of silane are recorded on a Fourier transform spectrometer with a specially made multipass cell at a resolution of 0.01 cm-1. The spectra show a striking symmetrical top rotational structure, which has been predicted as the limiting case of a spherical top exhibiting local mode behavior, and provides an excellent chance to study the local mode rotational structures in detail. This article reviews the interpretation and analysis of the spectra in both local mode and normal mode pictures. The intramolecular dynamics following initial single bond excitation is also discussed.