Materials for Multibit‐per‐Site Optical Data Storage

An approach for multibit‐per‐site optical data storage has been proposed and demonstrated using mesostructured composite films incorporated with uniformly dispersed photoacid generator and pH‐sensitive dye molecules. Upon light illumination, photoacid generator molecules produce acid, which induces a change in the absorption property of pH‐sensitive dye molecules. Because the amount of the generated acid is proportional to the illumination time, the resulting change in the absorption property of mesostructured composite films varies as a function of the illumination time. This function between the absorption property of mesostructured composite films and the illumination time can be used for multibit‐per‐site optical data storage. Recording is performed by using certain discrete values of the illumination time to represent information bits. Reading out is achieved by measuring the absorbance of composite films at a particular wavelength, from which the stored information bits can be determined. In general, N‐bit‐per‐site storage can be realized using 2^N discrete values of the illumination time. This multibit‐per‐site approach for optical data storage is compatible with the current single‐bit‐per‐site technology used for compact disks and digital versatile disks, and will provide significantly larger optical storage capacity. It is also suitable for two‐photon multilayer optical data storage if the photoacid generators and pH‐sensitive dyes are properly designed.     

Effect of illumination uniformity on GaAs photoconductive switches

The dynamic behavior of a GaAs photoconductive switch was studied with an electro-optic imaging system during the first 2 ns after optical illumination. The switch behavior changed as a function of the spatial distribution of the optical illumination. Symmetric and asymmetric illumination schemes were investigated experimentally with our electro-optic imaging system. The electric fields were significantly enhanced in the regions of low photo-carrier density. Approximately 1 ns after illumination the simple longitudinal variation of the electric field gave way to nonuniform transverse structure. The experimental results were modeled by treating the switch as an integral part of a transmission line consisting of discrete elements. The experimental results matched the predictions of the transmission-line model in terms of the electric-field enhancements and efficiency     

光吸收调制微加工技术中偶氮材料光吸收率的时间变化特性

基于偶氮材料光吸收调制的高分辨率微加工技术近年来引起了极大关注。为揭示该技术中偶氮材料光吸收调制的机制,结合偶氮材料光致异构原理,利用偶氮材料的光吸收理论模型,数值模拟了偶氮材料光吸收率的时间变化特性。以典型偶氮苯染料分散黄7(Disperse Yellow 7-DY7)为例,分别开展了在365 nm光束单独作用和365 nm与532 nm双光束共同作用下,不同厚度DY7薄膜在365 nm光吸收率的时间变化特性实验研究。结果表明,在365 nm光束作用下,偶氮苯材料对365 nm光吸收率因光致异构效应发生了明显改变,而实验中532 nm光束的热效应对偶氮苯材料的光吸收率有显著的影响。     

皮秒激光脉冲触发下光电导开关响应时间的理论计算

本文采用计算机数值分析的方法,分析了激光脉冲的能量、宽度、半导体对光的吸收系数、半导体的表面复合、体复合以及俄歇复合等因素对光电导开关响应时间的影响。结果表明,光电导开关的响应虽然很快,但与光脉冲并不完全同步,而有一个短的时间滞后。     

激光控制的半导体加载波导开关研究

本文提出了一种新型毫米波波导开关－激光控制的半导体加载波导开关。这种开关具有插入损耗小，开关动态范围大，单模带宽宽，响应速度快等优点，同时，还提出了“有耗介质盘”的概念，从理论上对这种开关特性进行了分析，理论与实验吻合较好，预计，这种结构在高功率系统中有潜在应用前景。     

High photosensitivity and low dark current of photoconductive semiconductor switch based on ZnO single nanobelt

Photoconductive semiconductor switch (PCSS) based on ZnO single nanobelt (NB) was fabricated by controlling the concentration of mixed solution and using the probe technique, and applied into a test circuit to control the circuit state. The current-voltage characteristics and voltage spectra were investigated by system source meter and oscillograph, and the results show that the PCSS is of high photosensitivity of ∼10⁴, low dark current of ∼10⁻³ μA, low power consumption of ∼2.45 μW, typical rise time 0.12 s, and decay time 0.15 s. Within the wavelength range of 280-340 nm, the shorter the wavelength is, the higher the voltage response is. The test circuit state conversion between “1” and “0” is obviously corresponding to UV illumination “on” and “off”. The high photosensitivity and low dark current of PCSS can be reasonably explained by using the view point of light absorption and oxygen chemisorption mechanism.     

GaAs半导体对1.06m激光的吸收响应

人射光脉冲波长为1064nm时，GaAs光导开关上的直流电场强度为10~3V/Cm。讨一论了恒定光强和高斯光强时，GaAs杂质吸收载流子浓度随时问变化;将高斯光强时的模拟结果同实验相比较，二者吻合很好。     

Recovery time for a silicon waveguide all-optical switch

Dye laser pulses were used to switch the propagation path of an infra-red (λ=1.3 μm) beam propagating in a planar silicon waveguide. Recovery time ranged from 1.2 to 15 ns, depend on both the pulsed laser wavelength and the illumination geometry     

GaAs半导体对1.06μm激光的吸收响应

入射光脉冲波长为1064nm时,GaAs光导开关上的直流电场强度为10^3W／cm。讨论了恒定光强和高斯光强时,GaAs杂质吸收载流子浓度随时间变化;将高斯光强时的模拟结果同实验相比较,二者吻合很好。     

吸收因子对砷化镓高功率高速光导开关延迟时间的影响

本文用由于禁带变窄引起的吸收边漂移造成的电子吸收来研究了砷化镓高功率高速光导开关的延迟时间,给出了初始开态场、照射激光波长和温度对延迟时间的影响的简单公式.结果表明开关的半导体片对照射激光的吸收因子增大了开关的延迟时间,在计算中应该加以考虑.     

太阳能与市电互补照明控制器的研究

文中介绍了一款以单片机为控制核心的太阳能与市电互补照明系统控制器的设计。控制器通过对蓄电池充电开关、放电开关和市电供电开关的控制,实现了系统中蓄电池管理和系统运行控制等功能。本文对该控制器的工作原理、硬件配置、软件设计、功能进行了详细论述,对其功能和工作特性进行了测试分析。结果表明,控制器各项功能完成良好,具有较高的实用价值和良好的应用前景。     

Photothermal Bimorph Actuators with In‐Built Cooler for Light Mills,Frequency Switches,and Soft Robots

Photothermal bimorph actuators are widely used for smart devices, which are generally operated in a room temperature environment, therefore a low temperature difference for actuation without deteriorating the performance is preferred. The strategy for the actuator is assembling a broadband‐light absorption layer for volume expansion and an additional water evaporation layer for cooling and volume shrinkage on a passive layer. The response time and temperature‐change‐normalized bending speed under NIR, white, and blue light illumination are at the same level of high performance, fast photothermal actuators based on polymer or polymer composites. The classical beam theory and finite element simulations are also conducted to understand the actuation mechanism of the actuator. A new type of light mill is designed based on a wing‐flapping mechanism and a light‐modulated frequency switch. A fast‐walking robot (with a speed of 26 mm s^?1) and a fast‐and‐strong mechanical gripper with a large weight‐lifting ratio (≈2142), respectively, are also demonstrated.     

Operation of p-n Junction Photodetectors in a Photon Flux Integrating Mode

A technique for operating a p-n junction photodiode in a photon flux integration mode is described. In this mode the p-n junction is charged to a reverse voltage (less than its breakdown voltage) and then open-circuited. The voltage across the junction, with zero incident illumination, will decay at a rate that is independent of junction area. Time constants in the order of seconds may be achieved with silicon planar structures at room temperature. Under illumination, the rate of decay of charge depends linearly on the intensity of the incident illumination, so that the total charge removed is proportional to the time integral of illumination. Operation of p-n junction photodiodes is analyzed for this mode and boundary conditions are established. A practical structure utilizing this mode of operation is discussed. This structure makes use of the nearly ideal switch characteristics of an insulated gate field-effect transistor to periodically sample a photodiode. Advantages offered by this device structure include 1) linear dependence of signal charge on light intensity over several orders of magnitude; 2) electronically controllable sensitivity; 3) ease of integration into arrays for image sensing.     

SiC光控异质结达林顿晶体管的导通机理

利用窄能隙SiCGe三元合金，采用SiCGe/SiC pn异质结产生基极光电流方法，提出了新型SiC光控达林顿异质结晶体管功率开关结构，并用二维数值模拟软件对其导通机理进行了研究. 分析结果表明，SiC光控异质结达林顿晶体管在近红外区内具有明显光控开关特性，其饱和导通压降为4.5V左右，且宜于强光工作.     

基于非理想克尔介质的弧形波导全光开关

本文用有限差分光束传播法（FD－BPM）模拟并给出了基于理想克尔介质的弧形波导全光开关的开关特性曲线,分析了克尔介质中的非克尔非线性效应。用FD－BPM就非线性饱和以及背景吸收对弧形波导全光开关特性的影响进行了模拟,模拟结果表明,背景吸收和非线性饱和会减少弧形波导全光开关的开关次数,增加弧形波导全光开关的开关功率,导致全光开关的开关特性恶化。     

Light absorption distribution of uterine tissue filled with strong scattering medium irradiated by diffused light source

Determining the light absorption distribution (LAD) of uterine tissue helps the detection of endometrial carcinoma. In this work, a 3-dimensional optical model of the human uterus is proposed and examined. The model is filled with strong scattering medium (undiluted raw and homogenized milk, URHM) or air at 630 nm and 800 nm wavelengths. Monte Carlo simulations are used to find the absorption profiles of photons by transcervical laser illumination, with a cylindrically diffused light source (CDLS) or spherically diffused light source (SDLS). The results show that 800 nm is a good laser wavelength value for the detection of endometrial carcinoma by photoacoustic imaging (PAI). At the same time, the shape of the light source becomes less important in a relatively large cavity. The impacts of different scattering coefficients of CDLS on the irradiated area are demonstrated. Strong scattering medium is helpful to the illumination of the uterus cavity.     

非晶As2S3半导体薄膜在激光作用下的性能及结构研究

在激光辐照或退火作用下 ,As2 S3非晶半导体薄膜的光学吸收边出现红移现象 ,并且随着激光功率的增大和辐照时间的延长 ,红移值增大 ,并最后达到饱和。这种红移在先经过退火处理再激光辐照的薄膜中是可逆的。从扫描电镜的形貌图中也可以看出 ,经激光辐照后 ,薄膜表面有晶相出现 ,且随着激光功率的增加 ,晶相出现增多。As2 S3非晶半导体薄膜中光致效应的产生是由于光致结构变化所致 ,对其产生原因 ,进行了机理分析     

Absorption Dynamics in All-Optical Switch Based on Intersubband Transition in InGaAs–AlAs–AlAsSb Coupled Quantum Wells

We developed a pigtailed fiber module including an intersubband transition all-optical switch using InGaAs-AlAs-AlAsSb coupled double quantum wells and studied the absorption saturation dynamics. An increased extinction ratio was obtained by optimizing the delay time between control and signal pulses due to the reduced effect of two-photon absorption. An extinction ratio of 10 dB was obtained for a fiber input pulse energy of 16 pJ (200-fs pulsewidth). The absorption recovery time varied from 600 fs to 2 ps depending on the control pulse energy     

低串扰载流子注入型光开关的设计

针对载流子注入马赫-曾德尔干涉型光开关,提出使用输出比可调的3dB耦合器,补偿相移臂上通过载流子注入实现π相位调制所产生的吸收损耗,从而降低光开关的串扰。使用传输矩阵方法计算分析了载流子注入所伴随的吸收损耗对光开关串扰的影响,同时计算了可调3dB耦合器对光开关串扰性能的改进。计算结果表明,可调3dB耦合器的引入可以有效补偿相移臂的吸收损耗,对改善光开关的串扰性能有着明显的作用。     

2×2多模干涉光开关的设计与制作

以多模干涉耦合器为主体,通过载流子注入效应所引起的折射率改变来调整二重像之间的相位差,当折射率下降所引起的相位改变达到π相位时完成开关功能。在AlGaAs/GaAs/AlGaAs外延材料上,利用两步湿法腐蚀工艺,实际制作了2×2光开关并进行了测试。测试结果表明,工作在1.55μm波段,当注入电流达到160mA时,完成了开关功能。