基于Z扫描系统的石墨烯非线性吸收特性研究

利用Z扫描系统研究了多层石墨烯非线性光学吸收特性。结果表明多层石墨烯在激光作用下具有反饱和吸收特性,且非线性折射系数为正。随着层数增大,非线性光学吸收系数减少得慢一些。基于微观尺寸效应,2～5层石墨烯的叠层方式也会影响到非线性吸收系数的值。另外,激光的强度、中心波长和脉宽等因素都会影响样品非线性光学吸收系数的结果。石墨烯具有非常优良的非线性光学特性,为其制成非线性光学器件提供了有效的实验依据。     

纵向扫描法测量非线性折射率和吸收的理论分析和测量结果

本文以薄样品的分析为基础,采用高斯分解方法,在一定近似条件下,对纵向扫描进行严格的理论推导,获得了远场光阑归一化透过率的数值解析表达式.利用所得表达式,由测得的归一化透过率曲线可同时获得非线性折射率和非线性吸收的大小和符号.对非线性吸收和极值点的讨论进一步证明了结果的准确性.最后简要介绍了一种自行设计的全自动纵向扫描测试系统,并对CS₂标准样品进行了闭孔测量.测得CS₂的非线性折射率大小与国际报道完全一致.     

基于衍射理论的大非线性相移Z扫描研究

以衍射理论为基础,建立了强非线性吸收下,非线性介质对高斯光束的衍射模型.数值计算表明,折射相移的增大使峰的透过率增强而谷的透过率趋于饱和;而吸收相移的增大使峰的透过率被抑制而谷的透过率增强.相移比值是决定谷-峰结构存在与否的关键.在一定的输入功率下,远场输出功率并不是完全随着非线性吸收系数的增大而增大.该理论的近似条件只要求是薄样品,具有更好的适用性.     

大非线性相移下光学非线性Z扫描特性的研究

采用高斯分解法(GD)对大非线性相移下的Z扫描特性进行了分析,通过对数值算法的优化,将GD推广到对脉冲入射激光下大非线性相移下的Z扫描理论分析.对不同条件下大非线性相移Z扫描曲线峰谷结构的比较,发现在大非线性相移的情况下,Z扫描曲线的峰和谷随透过光阑或入射光强变化表现出某些新的特性.随着透过光阑孔径的增加,Z扫描曲线峰的变化要明显快于谷的变化,而且在谷明显存在的情况下,峰很快消失.采用皮秒脉冲激光下的纯二硫化碳实验对理论结果加以验证,实验结果和理论分析相一致.我们的分析结果对大非线性相移下Z扫描测量有一定的指导性意义,避免在大非线性相移下对Z扫描结果产生错误的分析.     

非线性折射率测量的Z扫描方法

描述了利用会聚的单光束灵敏地测量各种非线性介质的非线性折射率和非线性吸收系数的方法。被测样品放置于会聚高斯光束的光轴上（ｚ轴），样品在焦点附近沿ｚ轴移动，在远场处放置带有小孔的屏。通过小孔测量光束通过样品后的透过率，根据透过率与样品位置的关系，即可得到非线性介质的非线性折射率和非线性吸收系数，并能确定非线性折射率的符号（自聚焦或自散焦）。给出了若干测量结果。     

反饱和吸收激发态非线性材料的Z扫描分析

本文用速率方程理论分析了激发志光学非线性材料非线性吸收和折射,通过数值模拟讨论了激发态和基态吸收截面、折射度相互关系等参数对非线性吸收和折射性质的影响。并从理论上分析了C₆₀甲苯溶液的Z扫描实验曲线,它具有强非线性吸收和弱非线性折射。     

“绿色”液体激光介质的非线性光学特性研究

利用氧化钕和盐酸为原料制得Nd(phen)2Cl3(三氯二邻菲罗啉合钕),测得其光谱特性并以稀土氧化钕、苯甲酸和邻菲罗啉为原料制得绿色液体激光介质钕离子的配合物——NdB3 phen(三苯甲酸-邻菲罗啉合钕).利用飞秒激光器,采用单光束Z-扫描法研究了NdB3 phen的三阶非线性光学特性.结果表明:当入射飞秒激光脉冲...     

纳米微粒SnO2非线性光学特性的Z—扫描技术研究

利用Ｚ－扫描技术，以调ＱＮｄ：ＹＡＧ激光器作光源，首镒在非共振区域研究了ＳｎＯ２纳米微粒的三阶非线性光学性质，获得了三阶非线性极经系数ｘ＾（３）与双光子吸收系数β等重要依据，并对其非线性响应机制进行了探讨。     

测量慢弛豫介质的非线性折射率Z扫描方法

对非线性折射率慢弛豫介质的Z扫描理论进行了详细推导,得到了透射光场的表达式.分析表明:对于慢弛豫介质,其Z扫描过程也是非线性折射的累积过程.实验结果与理论分析一致. 关键词：     

Z—扫描技术及其应用

文章介绍了Ｚ－扫描技术的原理、特点及其应用，分析了单色Ｚ－扫描法测量非线性折射系数和非线性吸收系数，以及双色Ｚ－扫描法研究非简并非线性光学效应．     

Z-扫描技术与非线性光学材料性质的测量

介绍了Z-扫描技术的基本原理，以及Z-扫描技术在测量非线性光学介质的非线性折射率、非线性吸收系数和光学限制器等方面的应用，以细菌视紫红质(bR膜)、碘的酒精溶液和偶氮材料CN2为例，分别介绍了它们的测量结果，给出了提高Z-扫描灵敏度的改进方法，介绍了其发展装状况。     

强非线性吸收下高斯光束Z-扫描衍射理论模型

在同时考虑非线性折射和非线性吸收的情况下,借助光的衍射理论,研究了Z-扫描技术的衍射理论模型,分析了非线性折射和非线性吸收同时存在时Z-扫描曲线的形状特征和变化规律。数值计算表明,非线性吸收相移和非线性折射相移的比值是影响接收小孔输出光功率的重要因素。要想得到好的光限幅效果,应选取非线性相移比值远小于1或远大于2的非线性材料。     

Investigation of optical nonlinearities in Pd(po)2 by Z-scan technique

With nanosecond scale at a 532 nm wavelength, we firstly measured the nonlinear optical absorption and refraction coefficients of Pd(po)₂ complex by using Z-scan technique, here Hpo=1-hydioxy-2-pyridone. We describe an empirical expression for the case when nonlinear refraction is accompanied by nonlinear absorption to separately evaluate the nonlinear refraction and the nonlinear absorption by performing straightforward measurements with the aperture removed. The nonlinear optical response of Pd(po)₂ was determined by the linear decreasing irradiance-dependence. The nonlinear absorption originates from the near resonant two-photon absorption while the mechanism of the nonlinear refraction is the near resonant two-photon absorption transition enhancement. The linear increasing dependences of the optical nonlinearities on the incident irradiance arise from the population redistribution due to the near resonant two-photon absorption.     

Nonlinear refraction and nonlinear absorption of As2S3 aqueous solution

We report for the first time to our knowledge on the preparation of colloidal solution of chalcogenide semiconductor As₂S₃ by laser ablation and the measurements of its nonlinear-optical characteristics using Z-scan method at the wavelength of Nd:YAG laser radiation ( = 1064 nm, = 25 ns). The nonlinear refractive index was measured to be –7.5 × 10^–18 m² W^–1. Nonlinear absorption coefficient of chalcogenide solution was measured to be 1 cm GW^–1.     

强非线性吸收下高斯光束Z-扫描衍射理论模型

 摘要：在同时考虑非线性折射和非线性吸收的情况下，借助光的衍射理论，研究了Z-扫描技术的衍射理论模型，分析了非线性折射和非线性吸收同时存在时Z-扫描曲线的形状特征和变化规律。数值计算表明，非线性吸收相移和非线性折射相移的比值是影响接收小孔输出光功率的重要因素。要想得到好的光限幅效果，应选取非线性相移比值远小于1或远大于2的非线性材料。     

Saturated absorption and nonlinear refraction of silicate glasses doped with silver nanoparticles at 532 nm

The nonlinear optical characteristics of silicate glasses doped with silver nanoparticles are investigated by Z-scan technique using second harmonic radiation of picosecond Nd:YAG laser (=532 nm, =55 ps). The real and imaginary parts of third-order nonlinear susceptibility of silver-contained glasses were measured. It was found that the sign of Im ⁽³⁾was negative due to saturated absorption and the sign of Re ⁽³⁾ was changed from negative (self-defocusing) to positive (self-focusing) with growth of laser radiation intensity. The mechanisms responsible for saturated absorption and nonlinear refraction are discussed.     

高斯光束通过非线性折射和吸收介质的光强分布

以衍射理论为基础,推导并模拟了高斯光束通过非线性折射和吸收效应介质后的远场光强分布。结果表明:入射高斯光束引起的介质折射率变化和光束波前曲率影响介质出射面光束的径向调制相位,安装在焦点前的有自聚焦效应的介质和安装在焦点后的有自散焦效应的介质具有闪耀光栅的能力,使远场出现中心为暗斑外侧为亮环的衍射图样。非线性折射效应为主的介质,其非线性吸收效应的变化同时改变远场衍射图样的数目和光强值,但对于非线性吸收效应为主的介质,衍射图样的数目随吸收效应的变化不明显,吸收效应只影响光强值。     

Kramers-Kronig type of dispersion relation in nonlinear optics

The applicability of Kramers-Kronig (K-K) relation under nearly sharp resonant transition regime in narrow-gap semiconductors has been established and consequently, a generalized dispersion relation for nonlinear optical susceptibility of a dielectric is derived. This relation can be employed in the study of nonlinear optical processes in solids as well as in plasmas over a wide frequency spectrum.     

Effect of coupling between linear absorption and nonlinear absorption on Z-scan measurements

The contribution of multiphoton absorption to open-aperture Z-scan measurements is analysed by coordinate transformation. The approximate closed-form solution is obtained, which is suitable for application in higher-optical power regime. As an example, the coupling between linear absorption and two-photon absorption is discussed in detail.