CRYSTALLIZATION OF DIELECTRIC SPHERES IN LASER STANDING WAVE FIELD

Experimental study on crystallization of polystyrene spheres and SrTiO₃ particles in laser standing wave field is presented. The diameter of polystyrene, which are able to be trapped, is 7 times smaller than that reported by Burns, the corresponding lattice constant is reduced to 1.5 μm. The crystallization effect of SrTiO₃ particles with a refractive coastant of 2.5 in the visible range is observed for the first time. Based on the results above we believe that it is possible to construct photonic crystal with lattice constant extended to visible wave range by this method.     

条形GaAs半导体激光器的非线性温度特性

一、前 言 在通常的(AlGa)As条形半导体双异质结激光器的输出功率随注入电流变化的过程中,由于非线性扭曲现象的存在,限制了输出功率的动态范围,带来了使用的局限性。尤其在模拟调制的通讯系统中,对讯号引入畸变,在与光纤的耦合上也造成困难。因此,非线性问题的研究成为重要课题之一。 目前对非线性问题的研究大多在固定温度条件下进行[1-3].对于非线性现象在低温下随温度的变化关系叙述不多.然而对激光器低温特性的研究还是重要的[4].我们在低温的不同温度下对激光器的非线性现象进行了观察。定性作了初步探讨,以便从实验结果进一步了解…     

低频响及低采样频率下用布朗运动分析法测量光阱刚度

布朗运动法测量光阱刚度因其简便易行而成为光镊系统参数测量的一种常用的方法，但是由于在低频响或低采样频率时测量结果误差很大，所以主要用在频响及采样频率较高的情况下.将在功率谱分析及实验的基础上，讨论如何在低频响及低采样频率下，用布朗运动法测量光阱刚度. 关键词： 布朗运动 光阱刚度 光镊 功率谱     

STUDY ON LIGHT LOCALIZATION OF ONE-DIMENSIONAL DISORDERED MULTILAYER

Antimonite and cryolite are used as the high and low refractive index coating materials to be evaporated alternately to the glass substrates. All cryolite layers have the same thickness d/4n_a, and the thickness of antimonite layers varies randomly around an average value d/4n_b, with d=650nm, n_a and n_b their refractive indices. Three kinds of multilayer are prepared, they possess the same degree of thickness disorder, but different total lengths, i.e., 10, 15 and 21 perioda. We measure the transmission and reflection spectrum after the light passing through these multilayers. The exponential intensity variation versus total length is experi-mentally demonstrated, and the light localization length is then obtained. Our experimental results can be fitted very well with the numerical simulation. Based on the measured and calculated localization length, the effects of phase coherent: Bragg reflection and Anderson localization are discussed.     

Measurements of displacement and trapping force on micron-sized particles in optical tweezers system

A high-stability optical tweezers equipped with a high-precision measurement system of displacement and force is set up. The results show that this combination can be used to carry out quantitative measurements of small displacements and forces for micron-sized spheres. The precision of measurements has reached nanometers and piconewtons, respectively.     

光镊系统中微小颗粒的位移和所受力的测量

利用高稳定度的并配备了高精度位移和力测量装置的光镊系统，实现了对微米颗粒的纳米量级的位移和所受皮牛顿量级的力的定量测量.     

Effects of matrices on Mie scattering in the mid-infrared region

Various Mie scattering systems, each having a transparent matrix, are studied in the mid-infrared region. Our three theoretical scattering systems correspond to a lossless scatterer, an anomalous dispersive dielectric scatterer and a metal scatterer, each in a non-air usual matrix. The refractive-index effects of the matrix on scattering and extinction efficiencies in the mid-infrared region are found to be quite different in different cases. Although the non-air usual matrix reduces scattering and extinction efficiencies in the first kind of system, it may or may not help scatter and extinguish the mid-infrared radiation in the second, and it has little effect on them in the third.     

EFFECT OF SPHERICAL ABERRATION INTRODUCED BY WATER SOLUTION ON TRAPPING FORCE

Trapping force of an optical tweezers system with an oil immersion objective is calculated with a ray-optics model. Results indicate that the trapping force will be decreased as a result of the introduction of spherical aberration, which is caused by the refractive mismatch between objective oil and water, when the sample manipulated is suspended in a water solution. The effect of spherical aberration will be serious when the detection depth of the optical tweezers is enhanced.     

Zn2准分子的形成及其发射特性

通过光学抽运Zn(4s¹S₀—4p³P₁)共振线,在充有惰性气体的Zn蒸气中观察到两个连续的发射谱带。实验辨认它们可能归属于Zn₂准分子³∑_u⁺态,这与理论预言一致。研究谱带的时间与温度特性,以及惰性气体对谱带发射的影响。给出分子形成速率的上限和猝灭速率。结果表明,惰性气体分子在Zn₂准分子的形成及衰变中起了主要作用。 关键词：     

THE REFLECTIVE PROPERTIES OF BROADBAND OPTICAL MULTILAYERS

Binary multilayers with a certain kind of disorder may exhibit high reflection range over a very wide bandwidth. The dependencies of this bandwidth on the center wavelength, random layers sequence, refractive contrast of the coating materials, layer thickness errors and the angle of incidence have been studied numerically. Our simulations have shown that broadband reflectors can be designed for various applications. The reflective curves for staggered multilayers are also computed. The results show that the broadening effect of irregular multilayers is dominated by its degree of disorder. A broadband TiO₂-SiO₂ multilayer is fabricated. The measured width of the transmittance less than 1% for this multilayer covers 400 nm, from 700 to 1100 nm, which is just the tuning range of T_i: sapphire lasers.