可见/红外宽光谱分色片偏振调控的设计

针对光学系统中可见/红外宽光谱分色片的偏振特性,采用诱导透射法设计了满足偏振遥感光学系统能量要求的可见/红外宽光谱分色片,并对其偏振特性进行了分析.通过计算获得了透射带400～900 nm可见/红外宽光谱分色片的偏振情况,采用等效层理论在其基底背面设计了偏振调控膜系,对分色片透射带的偏振度加以调控.使用needle优化...     

不同气体环境下532nm激光诱导硅表面形貌的研究

研究了在不同气体环境下,利用532 nm Nd∶YAG纳秒脉冲激光累积辐照单晶硅表面形成的微结构,结果表明,在其他条件相同,背景气体不同的情况下,背景气体对硅表面形貌的形成起着重要的作用。具体分析了真空、N2和SF6 3种环境气氛下形成的微结构,结果显示,在SF6中形成的锥形微结构的数密度比在N2和真空中的大,并且锥形具有更大的纵横比;在N2、真空和SF6中形成的微结构尺寸依次减小。SF6气氛下,激光辅助化学刻蚀的效率比在真空和N2气氛中的高。另外,辐照区域边缘有波纹微结构形成,分析认为,该微结构的形成是由表面张力波的冷却导致的。     

脉冲控制量子系统的哈密顿量约化

探索了脉冲控制的含近简并能级的有限维量子系统的哈密顿量的约化．由一个非简并基态能级和几个近简并激发态能级组成的量子系统被一个短脉冲控制,目标是控制所有激发态的布居数之和．考虑了两个可以看成等价二能级系统的例子,当脉冲强度比较弱时,得到了原始系统和约化系统的简单关系;当脉冲强度比较强时,对于只含一个频率的脉冲,一阶近似的关系也是存在的．     

冷原子介质中基于相干诱导高反射带和高透射带的全光路由控制

以相干诱导光子带隙结构为工作基础,提出了一种可对两个弱光信号的传播路径同时进行动态调控的新型全光路由控制方案。利用描述光波在空间周期介质中相干散射的传输矩阵理论,结合描述单频激光与多能级原子共振相互作用的密度矩阵方程,计算了作为控制媒介的相干驱动超冷原子系综的稳态反射光谱和稳态透射光谱。结果表明,通过改变两个较强相干激光的空间模式、强度和频率等参数,可在探测跃迁共振频率附近建立反射率约为95%或者透射率约为95%的两个特殊频带。对这样的相干诱导高反射带和高透射带进行了实时动态调控,可根据需要引导两个不同频率的弱光信号进入指定的网络通道。该方案很好地满足了在量子信息处理领域对弱光信号进行全光路由控制时的低损耗和低形变要求。     

物理分析技术在无机氧化物晶体结构表征中的应用

以氯化锌和氢氧化钠为主要原料,采用简单液相法,通过改变反应液的组成,制备出了针状、棒状、片状和花状四种不同形貌的ZnO微/纳米晶体。应用X-射线粉末衍射仪（XRD）,扫描电子显微镜（SEM）、高分辨透射电子显微镜（HRTEM）及选区电子衍射仪（SEAD）对产物进行表征,获得了ZnO物相、形貌与微观结构的重要信息。     

Nano-Fabrication by Cathodic Plasma Electrolysis

Cathodic plasma electrolytic (CPE) techniques are new groups of coating processes, which can be used for fabrication of nanostructured layers on surface of a wide range of metallic substrates. The most exciting visible feature of these atmospheric-based plasma techniques is continuous sparking on processed surface inside an electrolyte. Unlike the anodic part of plasma electrolysis (usually known as plasma electrolytic oxidation (PEO) or micro arc oxidation (MAO)), which is commonly used for oxidation of light metals/alloys such as aluminum, titanium and magnesium, CPE techniques can clean and coat different metals and alloys such as steel, copper, and light metals/alloys with formation of wide range of nanostructures including complex carbides, carbonitrides, intermetallics, and even oxides. It has been observed that the properties of obtained layers depend on the characteristics of achieved nanostructures such as average size, distribution and average coordination number of nanocrystallites. Furthermore, the properties of the processed surface can be tailored by tailoring the nanostructure characteristics. There is limited literature available on the mechanism of CPE and its connection to the morphology of nanostructured layers. This article addresses the two important aspects of CPE, namely characterization of nanostructured layers and mechanism of cathodic plasma electrolysis, which are reviewed in accordance to the morphology of fabricated nanostructures.     

Statistical quality control for ternary ordinal quality data

The paper considers various aspects of statistical quality control by means of sample data received on a ternary ordinal scale. A new method for evaluating quality level and dispersion, free of any latent numerical scale assumptions, is proposed. The emphasis is on working with large samples, which enable the statistical analysis, estimation and control by the use of approximate analytical expressions of these measures to be considerably simplified. Two complementary studies demonstrate the usage of the proposed approach. Copyright © 2010 John Wiley & Sons, Ltd.     

Analytic investigation on the similariton transmission control in the dispersion decreasing fiber

By means of the similarity transformation, we discuss the generalized nonlinear Schrödinger equation exhibiting inhomogeneous dispersion, nonlinearity and gain or loss at the same time. Explicit bright and dark multi-similariton solutions are obtained. Based on them, we investigate transmission control using the dispersion decreasing fiber with potential applications to the design of high-speed optical devices and amplifiers and pulse compressors, and the development of tunable sources of amplitude modulated light.     

Triggering of high voltage discharge by femtosecond laser filaments on different wavelengths

The triggering and guiding of high voltage discharge by plasma filaments generated by 400 nm and 800 nm femtosecond laser were studied experimentally. The detailed diagnostics for characteristics of filaments, such as amount of free electrons, diameter and electron density, were performed using sonographic method, fluorescence imaging and resistivity measurement. A significant reduction of the breakdown voltage threshold due to the pre-ionization of the air gap by laser pulse filaments was observed. It is shown that the 400 nm laser pulses demonstrated stronger triggering ability than 800 nm laser pulse under same pulse energy. This behavior of 400 nm femtosecond pulse is connected to the rich population of highly excited particles in filaments.     

Subnatural linewidth in a strongly-driven degenerate two-level system

We observe linewidths below the natural linewidth for a probe laser on a degenerate two-level F → F′ transition, when the same transition is driven by a strong control laser. We take advantage of the fact that each level of the transition is made of multiple magnetic sublevels, and use the phenomenon of electromagnetically induced transparency (EIT) or absorption (EIA) in multilevel systems. Optical pumping by the control laser redistributes the population so that only a few sublevels contribute to the probe absorption, an explanation which is verified by a density-matrix analysis of the relevant sublevels. We observe more than a factor of 3 reduction in linewidth in the D₂ line of Rb in room-temperature vapor. Such subnatural features vastly increase the scope of applications of EIT, such as high-resolution spectroscopy and tighter locking of lasers to atomic transitions, since it is not always possible to find a suitable third level.