Purcell Effect and Nonlinear Behavior of the Emission in a Periodic Structure Composed of InAs Monolayers Embedded in a GaAs Matrix

Enhancement of spontaneous emission in a resonant Bragg quantum well (QW) structure with 60 periods of triple InAs monolayers embedded in a GaAs matrix is studied experimentally and theoretically. From measurements of the time‐resolved photoluminescence, besides the QW exciton at 1.47 eV, a specific super‐radiant (SR) emission demonstrating nonlinear properties is found. The SR mode shows a near‐quadratic dependence of intensity on excitation power, while its energy position follows the Bragg condition. It is revealed that the SR mode shows a peculiar non‐monotonic dependence of intensity on direction, with a maximum observed at approximately 40°. The enhancement in the SR emission at a specific direction is correlated well with suggested theoretical consideration of the modal Purcell factor for periodic quantum well structures.     

计算全息检测非球面干涉场的理论分析与实验结果

本文应用光学全息术及傅里叶光学的理论对计算全息图干涉检测非球面面形的光路及干涉场进行了理论分析,提出了其干涉场为不定域干涉的观点,并在实验中予以证实.     

急倾斜厚煤层掩护支架采煤法机械化问题的探讨

掩护支架采煤法是开采急倾斜厚煤层的有效方法之一,但回采工艺大多使用炮采。为进一步扩大急倾斜厚煤层掩护支架采煤法的适用范固,大幅度地提高技术经济效果,必须实现掩护支架下的采煤机械化。本文在总结分析国内外有关经验、资料的基础上,对掩护支架结构型式的改进和采煤机械化问题进行了初步的探讨,提出了设想方案。     

Approaches to improving critical current density of YBCO superconducting thick films deposited by electrophoresis

The irreversibility field (Hirr) of Y-based superconductor is much higher than that of Bi-based superconductor. Y-based superconductor is capable of maintaining stable electrical currents in high magnetic field and electric field, so it is a better suited mate-rial for electric-current applications. Commonly, the Y-based tapes comprise a YBCO thick film deposited on a flexible substrate, typically with an intermediate buffer layer, and an overcoat of noble metal. In this process, the interm…     

数字全息图变频采样研究

根据Whittaker-Shannon抽样定理,对菲涅耳全息图进行变频率采样,保证整个全息图各部分采样频率为该处相应空间频率的两倍,从而完全消除数字全息图由于采样冗余而带来全息图的信息冗余.并且,对变频采样后的全息图进行线性插值恢复即可获得良好的再现像质.实验和理论均证明了该方法的有效性和可行性,为全息图的信息存贮与传输提出一条新的思路.     

三基色计算全息图

介绍了三基色计算全息图的设计与制作，用白光光源照明该全息图，可以演示光的叠加，再现彩色图像并给出了理论分析和相应的实验结果。     

Compact, reliable asymmetric optical configuration for cost-effective fabrication of multiplex dot matrix hologram in anti-counterfeiting applications

This study presents a compact optical configuration that can generate a multiplex dot-matrix hologram with complex interlaced images for anti-counterfeiting applications on valuable paper. Varying the orientation of the interference plane can enable the multiplex hologram to be recorded without changing the interference angle of two laser beams. With its simple asymmetric optical setup, a multiplex hologram with many interlaced images can be efficiently fabricated, increasing the cost of imitation. Experimental details of the asymmetric optical setup are also described.     

Improvement of real time diffraction efficiency of NGD holograms by introducing electron donors

Nongelatin dichromated holographic film(NGD) is a new holographic recordingmaterial.Holograms recorded on this material have better environmental stability, higherdiffraction efficiency and stronger real time effect, etc..An experimental study to ascertainthe influence of two electron donors, namely,N,N-dimethylformamide(DMF) and dimethyl-sulfoxide(DMSO),on the real time diffraction efficiency(RTDE) of NGD holograms is car-ried out.The pressence of electron donors not only improves the sensitivity,but also enhancesthe real time effect greatly.RTDE of above 60% at±1 orders of NGD plane transimissiongrating is achieved by introducing electron donors.     

High longitudinal selectivity of shifting multiplexing in volume holograms

High longitudinal selectivity of the shifting multiplexing with spherical reference wave is proposed and demonstrated. A simplified method based on wave optics is used for calculating the selectivity, and the result fits well the experimental measurement. Under the paraxial condition, a simple formula for the longitudinal selectivity is introduced. With use of an object lens with effective NA=0.817, we obtain that an FWHM of selectivity is as small as 1 μm.     

计算全息图产生的锥面波在激光准直中的应用

本文提出了用计算全息图产生锥面波的方法.将全息图置于激光光路中,它的衍射图样中心在空间形成了一条准直线.文中对锥面波的传播、准直精度及准直距离作了理论分析,给出了实验结果.