Enhancement of Available Conversion Efficiency of Optical Parametric Amplifier in a Cascaded Photonic Crystal Structure

Using the cascaded structure of a linear and a second-order nonlinear photonic crystals, we realize a high-efficiency optical parametric amplifier in the case of exact phase matching. This proposal is verified using the slow-envelope nonlinear finite difference time domain numerical method. Compared with the case of the individual nonlinear photonic crystal structure, the oscillation threshold is decreased obviously; and the peak power amplification factor of the transmitted signal is enhanced more than 20 times.     

Localization and Threshold of Bistable Switching by Gap-Edge Shifting

We numerically investigate the localization behaviour of light propagation in a one-dimensional nonlinear photonic crystal (1D-NPC). It is found that the localization of a high gap-edge mode is better than that of a low one, so that the switching threshold of the 1D-NPC with plus Kerr L-layers is much lower than that with minus Kerr H-layers. For a structure of 16 periods, the threshold of the structure with nonlinear L-layers is about 1/10 of that with nonlinear H-layers in the same level of nonlinear refractive coefficient.     

纠正两个错误认识

错误之一:磁通量跟线圈的匝数成正比. 这是一个较为流行的误解.有这样一道题目:如图1所示,一匝线圈的面积为S,垂直于磁场方向放置,磁场是磁感强度为B的匀强磁场,求穿过线圈的磁通量Φ1是多少.若把线圈换成N匝线圈,面积和放置方式都不变,再求穿过整个线圈的磁通量Φ2是多少.     

光谱法测量极化聚合物的电光系数

本文利用偏振光谱测量了极化聚合物的电光系数,分析了测试原理,理论分析与实验结果一致。     

飞秒激光所致金纳米粒子析出的玻璃非线性吸收

依据Z-scan技术,使用波长532nm的纳秒脉冲,研究了通过聚焦的飞秒脉冲诱导并辅以热处理得到的金纳米粒子析出的玻璃的非线性吸收.观察到金纳米粒子析出的玻璃具有饱和吸收特性.根据局域场效应,对实验结果拟合,得到在接近表面等离子体共振激发情况下,金纳米粒子三阶极化率虚部分别为Imχ(3)m=57×10-7esu.玻璃样品中金纳米粒子的非线性响应主要起源于热电子贡献. 关键词： 带内跃迁 带间跃迁 热电子贡献     

Measurements of total absolute collision cross section of ultracold Rb atom using magneto-optic and pure magnetic traps

The implementation of a technique to measure total collision cross sections using laser-cooled rubidium atoms along with the introduction of room-temperature background gases, confined in both magnetooptic and magnetic traps, is proposed. Atom loss from the trap and total collision cross section can be inferred from the knowledge of the density of background gases. The measured cross sections from the magneto-optic and magnetic traps are represented, compared, and found to be significantly different. The measurements using this technique have a very small error in the range of approximately 2%-7%.     

Generalization and propagation of spiraling Bessel beams with a helical axicon

A generalized type of spiral Bessel beam has been demonstrated by using a spatially displaced helical axicon (HA).The topological charge of the spiraling Bessel beams is determined by the order of the input Laguerre-Gaussian (LG) beam and the topological charge of the HA.The obtained spiraling Bessel beams have an LG type of modulation along their propagation direction and exhibit annihilation-reconstruction properties.Theoretical analysis is presented,including that of the stability,propagation distance,topological charge,and spiraling dynamic characteristics.The mathematical and numerical results show that the propagation distance and helical revolution of the spiraling Bessel beams can be controlled through choosing appropriate radius of the HA.     

Retraction notice to Measurements of total absolute collision cross section of ultracold Rb atom using magneto-optic and pure magnetic traps [Chinese Optics Letters 9,060201(2011)]

This article "Measurements of total absolute collision cross section of ultracold Rb atom using magneto-optic and pure magnetic traps",which was published on Chinese Optics Letters(9,060201(2011)) has been retracted at the request of the authors.     

一维非均匀Kerr介质的传输矩阵算法

研究了一维非均匀Kerr介质的子层逆向递推传输矩阵算法,给出了数值实现方案.此方法可以方便而精确地模拟非均匀Kerr介质的传输行为.应用此算法模拟一维Kerr缺陷光子晶体的光学双稳开关过程时, 得出了和非线性时域有限差分方法相一致的结果.