克尔介质中脉冲宽度对瞬态热光非线性效应的影响

在纳秒时域，研究了激光脉冲宽度变化对克尔介质中瞬态热光非 线性效应的影响.通过不同脉冲宽度τp下得到的二硫化碳 苯胺黑溶液的Z_scan实验结果，对瞬态热光非线性效应和光克尔效应的共存过程进行了分析 .随着脉冲宽度的增加，观察到了热光非线性效应从瞬态到稳态变化过程和Z_scan峰谷特性 的转变.同时，从声波的传播方程和光波的非线性传播方程出发，用数值计算方法模拟了这 一非线性过程，结果表明数值模拟结果和实验结果是相符的. 关键词： 瞬态热光非线性效应 脉冲宽度 Z_scan 克尔效应     

厚非线性介质瞬态热光非线性效应的研究

瞬态热光非线性效应是指由脉冲宽度可以和非线性效应的建立时间相比拟的纳秒脉冲激光入射产生的热光非线性效应.用Zscan法测量了不同厚度、不同束腰半径碘的酒精溶液的瞬态热光非线性效应曲线.从声波的传播方程和光波的非线性传播方程出发,用数值计算方法模拟了这一非线性过程.并对实验结果和数值模拟结果进行了比较 关键词： 瞬态热光非线性效应 非线性光学 数值计算     

相位物体$lt;i$gt;Z$lt;/i$gt;-扫描研究金属簇合物［$lt;i$gt;Tp$lt;/i$gt;*W($lt;i$gt;μ$lt;/i$gt;$lt;sub$gt;3$lt;/sub$gt;-S)$lt;sub$gt;3$lt;/sub$gt;Cu$lt;sub$gt;3$lt;/sub$gt;$lt;i$gt;Py$lt;/i$gt;$lt;sub$gt;3$lt;/sub$gt;($lt;i$gt;μ$lt;/i$gt;$lt;sub$gt;3$lt;/sub$gt;-Br)］($lt;i$gt;PF$lt;/i$gt;$lt;sub$gt;6$lt;/sub$gt;)/DMF溶液的瞬态热致非线性折射

在纳秒时域,采用相位物体（PO）Z-扫描技术研究了一种新型金属簇合物溶液的瞬态热致非线性效应.该方法的最大优点是很容易区分瞬态热致非线性折射和三阶非线性折射.本文利用PO Z-扫描和传统Z-扫描研究了在8 ns脉宽、不同能量激光脉冲作用下［Tp*W（μ₃-S）₃Cu₃Py₃（μ₃-Br）］（PF₆）/DMF溶液的光学非线性.从声波方程和热传导方程出发,对实验结果进行了理论分析和数值模拟,理论值和实验结果很好的吻合.研究结果表明,样品溶液的非线性折射主要来源于瞬态热致非线性效应. 关键词： Z-扫描')" href="#">相位物体 Z-扫描 瞬态热致非线性折射 光克尔效应 DMF     

LN晶体自散焦到自聚焦转换的耦合理论分析

对铌酸锂晶体进行了三阶非线性折射系数测量的Z扫描实验和光折变非线性系数测量的时间扫描实验。为了分析时间分辨扫描曲线的特点，基于非线性介质中光折变非线性与三阶非线性光学效应的耦合作用，引入非线性折射率随时间变化的表达式，分析了空间亮孤子的形成过程，进而揭示了其在一定条件下从自散焦到自聚焦转换的动态行为的物理机制,得到了与实验现象相一致的结论，并说明了自聚焦光折变晶体中可能存在稳定的暗空间孤子。     

基于光克尔门空间扫描单次激光信噪比测量

提出一种基于光克尔门空间扫描的单次激光信噪比测量方法.在该方法中,门光和探测光在光克尔介质中正交传输,通过光克尔门对探测光的空间扫描实现激光信噪比测量.采用该测量方法进行了单次激光信噪比测量的实验研究,测得时间窗口和分辨率分别为88.2ps、2.7ps.由于取样门是由光克尔效应来控制,因此该激光信噪比测量方法对于待测激光的波长没有限制.     

基于瞬态光克尔效应的超快光学快门技术

系统介绍了几种基于瞬态光克尔效应的超快光学快门技术,包括传统的光克尔双折射快门技术,瞬态光栅快门技术,以及利用瞬态克尔透镜效应的光学快门技术。这些技术都是在泵浦-探测的实验配置基础上,利用门控光对克尔介质折射率的瞬态调制导致的信号光的相位（偏振态）、传播方向或光束发散角等光学特性的改变实现对信号光的超快时间分辨测量。对比讨论了这些超快快门技术的工作原理和实验配置,结果表明瞬态光束偏折快门技术相比其他快门技术具有无偏振配置要求、无相位匹配条件、超宽带光谱响应范围的特点,在光与物质相互作用的超快动力学研究中具有更为广阔的应用前景。     

可溶性碳纳米管Z扫描实验研究

以可溶性碳纳米管为研究对象，进行了Z扫描实验.实验中通过改变样品的参量，研究了材料在不同浓度和不同厚度下的Z扫描曲线特性；实验分别在532nm和1064nm的激光下进行，并分别进行了开孔和闭孔实验.材料的闭孔Z扫描曲线没有明显的峰谷对称结构，而开孔Z扫描曲线呈现关于原点对称的单一谷形状，表明样品存在较强的非线性吸收效应，非线性吸收可能是其主要的光限幅机理.     

相位物体Z-扫描研究金属簇合物[Tp*W(μ3-S)3Cu3Py3(μ3-Br)](PF6)/DMF溶液的瞬态热致非线性折射

在纳秒时域,采用相位物体(PO)Z-扫描技术研究了一种新型金属簇合物溶液的瞬态热致非线性效应.该方法的最大优点是很容易区分瞬态热致非线性折射和三阶非线性折射.本文利用PO Z-扫描和传统Z-扫描研究了在8 ns脉宽、不同能量激光脉冲作用下[Tp*W(μ3-S)3Cu3Py3(μ3-Br)](PF6)/DMF溶液的光学非线性.从声波方程和热传导方程出发,对实验结果进行了理论分析和数值模拟,理论值和实验结果很好的吻合.研究结果表明,样品溶液的非线性折射主要来源于瞬态热致非线性效应.     

CS_2飞秒超快非线性特性的实验研究

采用中心波长800 nm、脉宽30 fs的超短激光脉冲,通过飞秒光开关技术对CS_2的飞秒超快非线性特性进行了实验研究.在探测光强与抽运光强比为1∶10时,得到了较理想的光克尔时间分辨曲线.通过实验测定的光克尔信号强度与激发光和探测光偏振方向夹角的依赖关系表明:30 fs的超短激光脉冲激发CS_2的克尔信号主要是源于光诱导双折射效应,而非用200 fs的超短激光脉冲时来自瞬态栅的自衍射效应.     

基于光克尔门空间扫描单次激光信噪比测量（英文）

提出一种基于光克尔门空间扫描的单次激光信噪比测量方法.在该方法中,门光和探测光在光克尔介质中正交传输,通过光克尔门对探测光的空间扫描实现激光信噪比测量.采用该测量方法进行了单次激光信噪比测量的实验研究,测得时间窗口和分辨率分别为88.2ps、2.7ps.由于取样门是由光克尔效应来控制,因此该激光信噪比测量方法对于待测激光的波长没有限制.     

Concentration dependent nonlinear refraction in chloroaluminum phthalocyanine/ethanol solution

Nonlinear refractive properties of chloroaluminum phthalocyanine (CAP) in ethanol solution are studied using the Z-scan technique with picosecond (ps) and nanosecond (ns) laser pulses at a wavelength of 532 nm. A transition from self-focusing to self-defocusing in CAP solution excited by 10 ns pulses is observed during the decrease of its concentration. This transition is due to co-existing excited-state refraction and transient thermal lensing effects. The experimental results are described very well using the rate-equation model and the theory of transient thermal refraction in liquids. The refractive cross sections of the excited-state are also obtained.     

Determination of optical Kerr nonlinearity of a photonic bandgap structure by Z-scan measurement

Through analysis of the dispersion relation in a photonic bandgap structure, the effective optical Kerr nonlinearity that determines a Z-scan profile particularly near the stop-band edges, is derived. Near and inside the stop band, the nonlinear optical phase change that originates from an off-resonant response is converted into a change in nonlinear optical intensity through Bragg reflection. The Z-scan measurement of a cholesteric liquid-crystal photonic bandgap structure confirmed that off-resonant Kerr nonlinearity is responsible for the characteristic open-aperture Z-scan profiles near the stop-band edges.     

Theoretical study of saturable Kerr nonlinearity using top-hat beam Z-scan technique

Saturable Kerr nonlinearity is theoretically investigated by use of the top-hat beam Z-scan technique. The saturation intensity changes the nonlinear refractive profile and decreases the sensitivity of the Z-scan measurements, which were quantitatively analyzed. An empirical formula for the saturable Kerr nonlinearity, which gave the relationship between the light intensity and the peak-valley transmittance difference, was accomplished. A high-accuracy method to determine the nonlinear refractive index and the characteristic saturation intensity was proposed.     

Simultaneous measurement of pure-optical and thermo-optical nonlinearities induced by high-repetition-rate, femtosecond laser pulses: application to CS2

A simple experimental technique is presented capable of separating the contribution of purely optical Kerr effects from that of thermo-optical effects in the nonlinear response of materials under high-repetition-rate laser irradiation. The technique has been realized by combining the single-beam Z-scan method with the single-beam thermal lens measurement method. We demonstrate this technique by analysing the nonlinear response at 770 nm of CS₂ which exhibits cumulative thermal effects when irradiated by very intense femtosecond laser pulses at a 76-MHz repetition rate. Received: 3 November 1998 / Revised version: 4 January 1999 / Published online: 2 June 1999     

真空绝缘子脉冲表面电场在线测量系统的实现

基于Kerr电光效应,建立了用以对纳秒脉冲高电压作用下的真空绝缘子表面电场进行在线测量的实验系统。该测量系统由快脉冲高电压源、YAG激光器、同步控制系统、被测中空薄壁绝缘子及Kerr效应单元、光学相位差检测系统等部分构成。利用YAG激光器输出的激光脉冲,触发导通快脉冲高压源中的高压气体开关,使其给被测绝缘子试品上施加一个脉宽100ns的高压脉冲方波。利用同步控制,使得探测激光在试品上的脉冲方波达到幅值后,入射到Kerr腔体中对Kerr效应进行探测。从而实现了对绝缘子表面电场的在线测量,并给出了初步的测量结果。     

InP纳米颗粒的超快动力学和光学非线性

通过飞秒泵浦-探测方法测量了波长为800 nm时InP半导体纳米颗粒激发态的瞬态动力学过程。观察到一个快速的光致漂白建立和一个漂白的恢复过程,分析饱和吸收的来源可能是带填充效应引起跃迁的饱和吸收。对于漂白恢复中的快过程是由于自由载流子的弛豫,而慢成分是由于光激发载流子在很短的时间内受陷于表面态形成的限域载流子的弛豫。通过飞秒光克尔效应(OKE)方法测量材料的超快非线性响应曲线,计算了材料的光学三阶非线性极化率,分析了非线性的来源。     

Effects of solvent on nonlinear absorption properties of tetraphenylporphyrin compounds in the nanosecond regime

The nonlinear absorption properties of tetraphenylporphyrins (TPP) in different solvents and excitation intensities are investigated with nanosecond pulses by the Z-scan technique. The nonlinear absorption behaviour observed presents a distinct difference between in solvent mixtures and in pure solvents. A crossover from reverse saturable absorption (RSA) to saturable absorption (SA) and then again to RSA is observed with the increases of excitation intensity in chloroform and pyridine mixed solvents. However, porphyrin molecules in pure solvents show good RSA behaviour under the studied intensity range, no saturation absorption is observed with nanosecond excitation. Excited state absorption parameters and two-photon absorption coefficients are obtained by theoretical fit using rate equations for population densities in a seven-level energy scheme.     

纳米银颗粒掺杂铋酸盐玻璃的光谱与三阶非线性光学特性研究

采用新型的热化学还原法,制备了银纳米颗粒掺杂的铋酸盐复合玻璃材料。利用紫外-可见吸收光谱观察到了银纳米颗粒表面等离子谐振(SPR)吸收的峰值位移特性,用拉曼光谱表征了引入银纳米颗粒后玻璃的结构变化。借助飞秒激光脉冲激发下的Z扫描与光克尔闸技术,在近红外波段下研究了材料的三阶非线性光学特性。研究结果表明银纳米颗粒铋酸盐复合材料有着亚皮秒级的非线性响应时间,并且其非线性折射率γ在纳米颗粒的热电子效应以及局部场效应的影响下,较基质玻璃最高可以提升29倍。     

Discriminating thermal effect in nonlinear-ellipse-rotation-modified Z-scan measurements

We report that a modified Z-scan method by nonlinear ellipse rotation (NER) can be used to discriminate true nonlinear refraction from thermal effect in the transient regime and steady state. The combination of Z-scan and NER allows us to measure the third-order nonlinear susceptibility component without the influence of thermal-optical nonlinearity. The experimental results of pure CS(2) and CS(2) solutions of nigrosine verify that the transient thermal effect can be successfully eliminated from the NER-modified Z-scan measurements. This method is also extended to the case in which thermal-optical nonlinearities depend on a high repetition rate of femtosecond laser pulses for the N,N-dimethylmethanamide solutions of graphene oxide.     

基于克尔效应的真空绝缘子表面电场在线测量

克尔效应(Kerr Effect)作为一种电光效应,主要表现为:克尔介质在外加电场作用下,会使得入射到其中的探测光带有外加电场的信息.基于上述原理,设计并搭建了由快脉冲高电压源、YAG激光器、同步控制子系统、被测绝缘子及克尔效应单元、相位差检测子系统构成的真空绝缘子表面电场在线测量实验平台.通过对比性测量,观察到了真空绝缘子沿面带电导致的表面电场畸变现象.并进一步对绝缘子表面电场的畸变进行了时间分辨测量.