光参量振荡器及其在化学中的应用

光参量振荡器(缩写OPO)是利用非线性光学效应实现波长调谐的一种激光器,主要波段在红外、调谐范围宽且能任意连续调谐,峰值功率高,波长比较稳定,平均功率低,谱线宽,成本高。OPO已用于化学、光谱学、测污等。OPO由泵浦源、振荡腔,调谐机构组成,改变参量振荡晶体的折射率来实现波长调谐。我所已实现的OPO的调谐范围0.8—1.2μm、1.8—2.5μm、能量约0.5～1mJ/脉冲,采用电光调     

可调谐中红外OPO激光器研究

研究了一种中红外可调谐OPO激光器,泵浦源为输出能量200 mJ能量的1.06μmNd∶YAG激光器,OPO采用XZ平面内二类匹配的KTP-OPO,实现了信频光1.5～2.0μm、闲频光2.3～3.6μm的波长调谐,光光转换效率10%以上。     

W级中红外宽调谐光学参量振荡器的研究

报道了一个低阈值、宽调谐、中红外单谐振掺MgO的周期性极化LiNbO3(PPMgLN)晶体光学参量振荡器(OPO)。利用声光调Q的Nd:YVO4激光器作为泵浦源,采用外腔结构,在室温下实现了PPMgLN晶体的准相位匹配(QPM)OPO。OPO阈值仅为0.4 W(重复频率40 kHz,单脉冲能量10μJ,脉宽160 ns);在泵浦光为6.6W(重复频率40 kHz,脉冲能量165μJ,脉宽65 ns)、PPMgLN周期为30μm时,获得了1.13 W的3.61μm中红外脉冲激光输出,光-光转化效率达到17.1%,同时获得了880 mW的1.51μm信号光输出,并且通过改变晶体的周期,实现了闲频光3.13～4.19μm中红外宽带可调谐激光输出。重点讨论了闲频光的功率、调谐和脉冲特性以及功率稳定性问题。     

捷变频中红外光参量振荡器实验研究

介绍一种快速调谐非共线光参量振荡器(OPO)。通过快速改变泵浦光与OPO中非线性光学晶体光轴的夹角,实现OPO的波长精确和快速调谐,光束入射时间、角度、速度和方向均由计算机控制,保证OPO的快速精确调谐。输出中红外激光波长3.1～4.2μm,最大输出能量9.8mJ。捷变频速率可达3.5×1012Hz/ms。     

206～2．8μm KTP OPO实验研究

为了得到2.7 μm波段可调谐激光辐射,设计了信号光单谐振荡KTP光参量振荡器(OPO),给出了KTP OPO II(B)类相位匹配方式下的角度调谐曲线、有效非线性系数.KTP晶体切割角为θ=62°,ψ=0°,有效非线性系数为-2.97 pm/V.利用该KTP OPO实现了2.6～2.8 μm波段范围可调谐激光输出,用脉宽为16 ns的基模高斯光束1.064 μm激光泵浦得到了最大能量578 μJ,能量转换效率达1.7%.     

2．6～2．8μm KTP OPO实验研究

为了得到2.7 μm波段可调谐激光辐射,设计了信号光单谐振荡KTP光参量振荡器(OPO),给出了KTP OPO II(B)类相位匹配方式下的角度调谐曲线、有效非线性系数.KTP晶体切割角为θ=62°,ψ=0°,有效非线性系数为-2.97 pm/V.利用该KTP OPO实现了2.6～2.8 μm波段范围可调谐激光输出,用脉宽为16 ns的基模高斯光束1.064 μm激光泵浦得到了最大能量578 μJ,能量转换效率达1.7%.     

光参量振荡器(OPO)在主动红外化学毒剂遥测中的研究进展

光参量振荡器(OPO))连续的调谐能力以及固体激光器在军事应用中的诸多优点，使OPO技术在主动红外化学毒剂遥测的应用研究近年来成为十分活跃的领域之一。在8～12μm的红外光谱区目前已发展了几种连续可调谐的OPO激光系统，能量输出在1mJ／脉冲水平的实验样机已经实现。为了达到探测距离为1～3km，化学毒剂激光遥测系统必需具有足够的信噪比，即要求单脉冲的激光能量应提高到2～10mJ／脉冲或更高。发展的趋势是研制新型的OPO晶体材料，降低非线性晶体的激发阈值，提高损伤阈值以及将初始的光子撕开，以多光子的形式进入8～12μm的光谱带以提高量子的转换效率。     

高转换效率的中红外BaGa_(4)Se_(7)光参量振荡器(特邀)EI北大核心CSCD

为抑制光参量振荡器(Optical Parametric Oscillator,OPO)振荡过程中信号光和闲频光向泵浦光的逆转换,首次采用在L型OPO腔的支路中插入信号光倍频晶体LiB_(3)O_(5)的(简称LBO)的方式,实现了BaGa_(4)Se_(7)(BGSe)OPO闲频光的高转换效率输出,当泵浦激光(1.06μm)能量为115 mJ时,闲频光(3.5μm)能量为16.18 mJ,光光转换效率为14.06%,斜效率为18.4%,这是目前已知1.06μm激光泵浦BGSe OPO最高的转换效率。模拟了不同泵浦能量下L型腔中有无LBO晶体时BGSe OPO腔内的三波波形,并给出了闲频光在实验中的输出波形。与传统OPO腔相比,所提出的L型OPO腔(含倍频晶体)在大能量泵浦条件下抑制了逆转换,可获得更高的闲频光转换效率。     

一套光学元件实现BBO光参量振荡器宽谱调谐实验研究

利用一套光学元件实现BBO光参量振荡器(OPO)0 4～2.0μm的宽谱调谐,采用了双棱镜环形腔和侧向抽运双晶体走离补偿直线腔.虽然两种腔型结构因为腔长长和高插入损耗,导致了高起振阈值,但都实现了BBO OPO信号光0.43～0.65μm,闲频光0.78～2.01μm无需更换腔片的连续调谐输出.     

利用KTP光学参量振荡器获得可调谐人眼安全激光

报道了用 Nd:YAG激光器二次谐波 532 nm抽运 KTP光学参量振荡器 (OPO)的实验结果 ,获得了对人眼安全的 1.53～ 1.84 μm和近红外 0 .74～ 0 .82 μm调谐激光输出 ,重复频率 10Hz。 OPO谐振腔采用π抽运结构 ,获得的最高总输出能量为 93m J,最高能量转换效率为 16 .5% ,并测量了光束质量和线宽。     

Improvement of the efficiency droop of GaN-LEDs using an AlGaN/GaN superlattice insertion layer

With an n-AlGaN(4 nm)/GaN(4 nm) superlattice(SL) inserted between an n-GaN and an InGaN/GaN multiquantum well active layer,the efficiency droop of GaN-based LEDs has been improved.When the injection current is lower than 100 mA,the lumen efficiency of the LED with an n-AlGaN/GaN SL is relatively small compared to that without an n-AlGaN/GaN SL.However,as the injection current increases more than 100 mA,the lumen efficiency of the LED with an n-AlGaN/GaN SL surpasses that of an LED without an n-AlGaN/GaN SL. The wall plug efficiency of an LED has the same trend as lumen efficiency.The improvement of the efficiency droop of LEDs with n-AlGaN/GaN SLs can be attributed to a decrease in electron leakage due to the enhanced current spreading ability and electron blocking effect at high current densities.The reverse current of LEDs at -5 V reverse voltage decreases from 0.2568029 to 0.0070543μA,and the electro-static discharge(ESD) pass yield of an LED at human body mode(HBM)-ESD impulses of 2000 V increases from 60%to 90%.     

A Common Source Input Cross Coupled Quad CMOS Mixer*

A CMOS doubly balanced mixer circuit is implemented with a source follower input and a cross coupled mixing quad. The circuit employs an all N-channel configuration and is suitable for high frequency applications. As a down-converter with an RF input of 2.0 GHz and an IF output of 200 MHz, the mixer demonstrates 9 dB of conversion loss with a corresponding input referred third order intercept of 0 dBm. As an up-converter with an IF input frequency of 400 MHz and an RF output of 2.4 GHz, the mixer demonstrates 14 dB of conversion loss.     

Staying Ahead of the Digital Tsunami: The Contributions of an Organizational Communication Approach to Journalism in the Information Age

This essay addresses the challenges facing journalism in the information age by advocating for the study of journalism from an organizational communication perspective. The communication field has maintained an illogical divide between journalism and organizational communication scholarship. First, I present an overview of subdisciplinary identities. Second, I argue for an organizational communication approach to the study of journalism and refer to an empirical study as an exemplar of this approach. Finally, I present ideas for future research regarding the study of journalism and these subdisciplines. This approach is applicable to settings like newspapers, television news, and other media organizations. Analyzing journalism from an organizational communication perspective can connect academic subdisciplines and aid practitioners in understanding a rapidly evolving media landscape.     

Monotone Span Program vs.Linear Code

Monotone span program(MSP) and Linear code(LC) are efficient tools to construct Linear secret sharing scheme (LSSS) for a given access structure.Since the size of an MSP or the length of an LC corresponds to the communicational complexity of an LSSS,one main motivation to study MSPs or LCs is the lower bound for their sizes or lengths.Therefore,it is one of the most important open problems how to efficiently construct an MSP or LC for a given access structure Γ with the smallest sizes or shortest length.Our contributions are:We extend TANG et al.'s result,showing that,for any given access structure Γ,there exists an MSP or an LC to realizeΓ if and only ifa system of quadratic equations has solutions;We utilize the relationship between LCs and MSPs to obtain the greatest lower bound on the row size and the column size of MSPs realizing a given Γ,as well as an upper bound on the column size of MSPs;We give an algorithm to construct an MSP with the smallest sizes.     

基于窄谱带模型的尾焰红外辐射计算

尾焰红外辐射的计算是飞行器红外辐射计算的重要环节.在尾焰流场工程计算模型的基础上,从燃烧的化学反应出发,解决了尾喷口处气体组分参数的计算问题,利用基于Malkmus窄谱带模型的C-G近似法得到了尾焰红外辐射的快速计算方法.仿真结果表明,该方法能够快速准确地计算出尾焰的辐射,能为红外制导导弹仿真中飞机目标红外辐射的计算提供有效途径.     

用热像仪测试面源红外诱饵面积的方法及误差分析

红外诱饵面积是决定面源红外干扰弹作战性能的关键指标,用红外热像仪可实现对面源红外诱饵面积的测试.本文针对红外热像仪的测量原理和计算方法,对面源红外诱饵面积的测试方法、数据处理方法及影响测量的误差因素进行了研究.该测试方法简单易行,在考虑影响因素后实施测量,并对测量数据进行大气透过率修正,可大大提高测量的准确度.     

某型航空相机的可靠性检测研究

可靠性检测是对设备规定性能的综合检验。航空相机的可靠性检测是其维护工作的一项重要内容。针对某型航空相机的特点,阐述了可靠性检测的基本概念、原理和方法,并给出可靠性检测结果的验收标准。     

基于半导体光放大器的非相干光源抗反膜的优化设计

对半导体光放大器(SOA)放大的自发发射(ASE)谱进行了实验和理论研究,并且分析了SOA端面反射率对ASE谱的谱宽以及平坦度的影响.结果表明,不恰当的抗反膜会严重减小输出光谱的带宽;而在采用具有宽带材料增益谱的有源区基础上,结合抗反膜的优化设计,则可以获得既宽又平坦的非相干光源.     

新一代的因特网--光因特网

光因特网是新一代的因特网，是网络发展的重要动向。本文从为什么会提出光因特网着手，介绍了什么是光因特网，其网络结构和帧结构，还分析了光因特网的好处。     

Cryptanalysis of an identity‐based authenticated key exchange protocol

Authenticated key exchange protocols represent an important cryptographic mechanism that enables several parties to communicate securely over an open network. Elashry, Mu, and Susilo proposed an identity‐based authenticated key exchange (IBAKE) protocol where different parties establish secure communication by means of their public identities.The authors also introduced a new security notion for IBAKE protocols called resiliency, that is, if the secret shared key is compromised, the entities can generate another shared secret key without establishing a new session between them. They then claimed that their IBAKE protocol satisfies this security notion. We analyze the security of their protocol and prove that it has a major security flaw, which renders it insecure against an impersonation attack. We also disprove the resiliency property of their scheme by proposing an attack where an adversary can compute any shared secret key if just one secret bit is leaked.