有机材料在光限制中的应用

对光限制器件的特性进行了简单的评述,并对由自散焦过程产生光限制的机理进行了分析.采用z-扫描方法对有机材料分散红一的非线性折射过程和光限制特性进行了实验研究.对其结果进行了分析讨论,这种分析对于以自作用效应产生最佳光限制效应是十分有用的.     

数值研究大功率激光器的大电流调制特性

本文对大功率激光器的大信号调制特性进行了分析。由于激光的弛豫振荡行为,会产生瞬态响应。在不同宽度的光限制层的条件下,对量子阱激光器的传输带宽进行了对比。光限制层越宽,载流子的传输效应越明显,导致传输带宽减小。大信号调制下,随着调制深度的增加激光峰值不断变尖锐。随着偏置信号的增大,光子密度也不断增大。     

C_(60)水溶胶的反饱和吸收与光限制效应

本文首次报道了C60水溶胶反饱和吸收和光限制效应的实验研究结果。利用532nm；15ns激光研究此样品的激光透过特性，观测到反饱和吸收过程，即实现了光限制效应。与C60苯溶液相比有较好的光限制效应。     

掺铁铌酸钾晶体中的光感生各向异性散射及其光学限制效应

光学限制器是光学系统的保护装置,其保护特性 是由光限制材料与光强或功率有关 的光学非线性效应所产生的,其中光折变晶体中的光感生散射便为该效应之一,多年来受到 世界研究者的广泛研究和关注。对于这类光感生散射,有人提出它是由晶体的表面和体散射 产生的,研究使用的晶体为 LiNbO₃:Fe、LiTaO₃、BaTiO₃,并使用固定的晶体样品和 聚焦透 镜间距。为了进一步探索该散射的产生机理,本文研究了掺铁铌酸钾晶体在激光照射下产生 的光感生各向异性散射特性,利用Z扫描技术测量了该晶体中的 光感生折射率变化,并对晶 体中光散射形成的光学限制特性进行了研究。分析表明该各向异性散射主要是由掺铁铌酸钾 晶体中光感生的柱面透镜效应所导致的。利用光折变晶体中光感生光散射效应的光学限制器 ,一方面可以通过改变晶体尺寸、透镜焦距、小孔光阑大小等来调整其性质,另一方面因其 利用的是低功率连续波激光进行工作,所以能够承受更大的功率和更长的寿命。     

液晶光阀的双稳态特性研究

测量了TB3639型液晶光阀在电压驱动下的光谱特性及其光学双稳态特性,并讨论其产生光学双稳态特性的非线性效应物理机制,分析了液晶光阀的光学双稳态特性不明显的原因.分析结果表明,扭曲角对液晶光阀的光学双稳态特性影响较大,由于TN型液晶光阀的扭曲角只有90°,导致其双稳态特性不是很明显,TB3639型液晶光阀在某一电压范围内存在光学双稳态特性.     

光子晶体光纤中超连续谱的产生

光谱超连续展宽在光通信中有重要的应用,用分步傅立叶法研究和分析了在光子晶体光纤中飞秒激光脉冲的传输特性和超连续谱的产生机理.结果表明:在光子晶体光纤中,超连续谱的产生是自相位调制、四波混频、交叉相位调制效应综合作用的结果,其中自相位调制效应起先导作用;光脉冲的峰功率、初始啁啾及光纤长度对超连续谱的形状和带宽有影响.     

基于SOA非线性的全光逻辑运算的理论研究

半导体光放大器(semiconductor optical amplifier,SOA)是具有优良非线性效应的光子器件.其非线性特性在光开关、波长变换、光逻辑运算中有重要的应用.从SOA载流子的速率方程和耦合波方程出发,经理论分析对SOA增益的非线性特性进行了研究和数值模拟,并通过连续光、脉冲光同时输入及两脉冲光同时输入两种情况,对SOA的交叉增益调制(XGM)这一重要的非线性效应进行了详细的研究和数值模拟.理论分析和数值模拟表明,基于SOA的这种非线性效应可以用来实现多种全光逻辑运算.     

光生伏打效应与光折变光栅的建立

带输运模型是目前被广泛接受的光折变理论.该模型以扩散机制为主.在某些情况下加上两个修正,即有外场时的漂移机制和光生伏打效应.其中光生伏打效应被考虑为等效于外加电场.而且常常被忽略了.作者认为光生伏打效应应当总被看作与扩散相并列的光折变机制,而且在铁电晶体.如LiNbO_3.中.光生伏打效应常常超过扩散而成为光折变过程的主要机制.文中将已有的光生伏打效应的唯像理论加以扩展,对产生光折变光栅的过程给出了较全面的分析.     

GaAs/GaAlAs量子阱在电场作用下光电流谱的研究

我们用室温和低温下电场下的光电流谱研究了 GaAs/AlGaAs多量子阱p-i-n 二极管的量子限制斯塔克效应.侧面光照下测量的光电流谱明显地反映出轻重空穴激子峰的偏振效应.对光电流谱和光致发光激发光谱进行对比发现,外加电场不仅影响光吸收,也影响多量子阱中光生载流子的漂移过程.光电流谱的线形用 P~-/n~+结的耗尽模型进行了分析,并计入了入射光强度在光传播过程中由于产生吸收跃迁而发生的衰减.光电流谱峰与激发光谱峰的斯塔克位移提供了多量子阱中电场分布的信息,并证明了耗尽区模型的正确性.     

高非线性光子晶体光纤的研究及应用

文章介绍了高非线性光子晶体光纤的特点及产生高非线性特性的基本原理,分析了在高非线性光子晶体光纤中产生超连续光谱和慢光效应的机理和其应用,并给出了国内利用文章作者研制的高非线性光子晶体光纤进行超连续谱和慢光试验的结果.     

A review of optical limiting mechanisms and devices using organics, fullerenes, semiconductors and other materials

We review nonlinear optical processes in various materials which can be utilized in passive optical limiting devices. Specifically, the mechanisms of reverse saturable absorption, two-photon and free-carrier absorption, nonlinear refraction and induced scattering are examined, and the implementation of these processes in optical limiting devices is discussed. The effectiveness of each approach depends on the specific application for the optical limiting device, and the advantages and limitations of each are addressed. Different materials, such as fullerenes, organometallics, carbon black suspensions, semiconductors and liquid crystals, all of which have been used in optical limiting devices, are discussed. In spite of the variety of nonlinearities, materials, and device configurations that have been used to implement passive optical limiters, no single device or combination of devices has yet been identified that will protect any given sensor from all potential optical threats.     

非线性光栅自调制光限幅器件研究

研制出一种三角槽型透明高分子聚合物光栅与该聚合物平板间填充有机非线性光学液体的夹层结构器件，具有非线性自调制光限幅功能。实验测得该器件对较弱的532nm波长的YAG倍频激光透过率大于60％。对较强激光透过率小于2％～3％。理论预期在激光波长400-700nm都有光限幅特性。且愈靠近532nm波长。激光限幅功能愈强。首次从实验上验证了该非线性光栅具有自适应宽带光限幅的功能。它不仅可以实现可调谐光限幅。且对所设计的激光波长，达到能量低于人眼安全阈值的高效激光防护成为可能。     

Nonlinear disordered media for broad-band optical limiting

We analyze broad-band limiting behavior in nonlinear structures that are, on average, periodic. Introduction of a controlled degree of randomness in layer thicknesses results in widening of the stopband. Light at all of the frequencies in this broadened effective stopband of the structure with randomly perturbed layer thicknesses exhibits true optical limiting-clamping of the transmitted intensity below a fixed level independent of incident intensity. We explore the impact of the degree of randomization and the strength of the nonlinear mechanism on the smoothness and regularity of the limiting spectrum and on the localization of the light within these cyclostationary media. Optical limiting in integrable devices is of interest in optical logic, signal processing, and personnel and sensor protection     

线性及非线性吸收热致光学限幅效应的讨论

本文分别对在连续和脉冲激光入射下，对由材料线性和非线性吸收产生在热致光限幅效应进行了研究，给出了产生最大光限幅效应的条件，为热效应光学限幅应用于光学器件的激光防护提供了理论依据。     

石墨烯-Au纳米复合体系的构筑及其光限幅效应

首先对Au纳米颗粒进行巯基修饰,再对其采用表面活性剂十六烷基三甲基溴化铵(CTAB)进行二级修饰,并将其自组装负载于石墨烯纳米毯(GNSs)上。通过紫外-可见吸收光谱证明Au纳米颗粒在石墨烯纳米毯(GNSs)上的成功负载。通过透射电子显微镜探明其微观结构,表明Au纳米颗粒在石墨烯纳米毯上呈现局部规整排列,其原因与石墨烯纳米毯自身的平整结构有关。采用开孔Z-扫描技术研究了负载Au纳米颗粒的石墨烯纳米毯的非线性光限幅性能,结果表明:其光限幅起始阈值明显下降,在低入射能量时即产生光限幅特性。并发现入射光强增大时非线性散射增强,说明非线性散射是产生复合体系的非线性光限幅效应的重要机理。     

金属-碳复合材料的制备及其非线性光学性质研究

基于浸渍法,成功制备了铁含量为10.7 wt％、铜含量为12.9 wt％的金属-碳复合材料,通过扫描电子显微镜、X射线粉末衍射谱、电感耦合等离子体原子发射光谱等手段表征了金属-碳复合材料的结构、形貌、晶型以及元素组成.通过开孔Z扫描实验和光限幅实验对该材料的非线性光学性质进行测试,该材料表现出优秀的反饱和吸收型非线性光...     

Efficient Nonlinear Absorbing Platinum(II) Acetylide Chromophores in Solid PMMA Matrices

Platinum(II) acetylides were incorporated into poly(methyl methacrylate) (PMMA) glasses to obtain solid‐state nonlinear optical devices. We report on device fabrication, structural, chemical, and mechanical properties, as well as the optical limiting capabilities of the final solids. Two different guest‐host systems are presented: 1) Dye molecules functionalized to be readily dispersed in methyl methacrylate (MMA) and subsequent in situ polymerization of the MMA yielding solid PMMA host matrices. 2) Dye molecules functionalized to copolymerize with MMA forming covalent bonds between the guest and the PMMA host matrix. A range of doped organic solids were prepared, reaching concentrations up to 13 wt% of the guest molecule. Raman spectra of the doped solid devices indicate that the chemical structure of the nonlinear dyes remains intact upon the polymerization of the solid matrix. Luminescence spectra confirm that the basic photophysical properties observed for the same solute molecules in THF are maintained also in the solid state. Optical power limiting (OPL) characterization reveal clamping levels for the dyes nonbonded to the solid host being less than 4 µJ at pulse energies up to 110 µJ at 532 nm (f/5 arrangement and 5 ns pulses), which is comparable to the performance of similar dyes in THF solutions. In contrast, the highly crosslinked solid possesses a higher clamping level (8 µJ) at the same nominal concentration.     

样品位置和光腰半径变化对折射型光限幅器性能的影响

本文以衍射理论为基础，通过数值计算，研究了以自聚焦和自散焦为基础的非线性折射型光限幅器的光限幅特性，探讨了样品盒的安装位置和入射光束腰斑半径的变化对折射型光限幅器工作性能的影响。结果表明：折射型光限幅器的光限幅特性曲线随激光输入功率的增加是衰减振荡的。光束聚焦差时，样品盒宜靠近焦面安装；光束聚焦好时，样品盒可稍远离焦面安装。对于自聚焦(自散焦)型非线性光限幅器，当样品盒安装在焦点左面(右边)半个瑞利范围内某位置时，透过率最小，限幅器可获得最佳限幅效果。     

Nonlinear optical limiter and digital optical switch by cascadednonlinear couplers: analysis

In this paper, an all-optical digital switch and a limiter are proposed and analyzed, both of which consist of several nonlinear directional couplers in series. These two devices utilize the nonlinear restraining effect of the nonlinear coherent coupler on its input power. In the devices, the OFF-ON extinction ratio, the output power fluctuation and the dynamic switching range all decrease with the number of the couplers in series increasing, and the output power level can be adjusted by varying the coupling length. The characteristics of these devices with different structures are discussed, and the numerical results show that the OFF-ON extinction ratio and the dynamic switching range of the optical switches can be less than -90 dB and 0.03P_c /100, respectively, and that the fluctuation of the limiting output power of the optical limiter can be less than 10^-7P _c