茉莉花茶乙醇溶液光学非线性研究

应用自位相调制和Ｚ扫描方法对茉莉花茶乙醇溶液的光学非线性特性进行了实验研究。测量了介质的非线性折射率ｎ２＝－７．９６×１０－６ｅｓｕ,非线性响应时间约０．７５ｓ,茉莉花茶乙醇溶液的光学非线性主要来源于介质的热吸收效应     

溶胶CdS毫微晶的双光子吸收及其量子尺寸效应

本文利用单光束透过率法研究了溶胶CdS毫微晶的双光子吸收。对于毫微晶尺寸为5.5～11.0nm的样品,测得其在波长510.6nm时的双光子吸收系数为1.31～5.24/GW,并由此得到相应的x~(3)为2.8×10~(-12)～1.1×10~(-11)esu。文中还从理论上分析了CdS溶胶的双光子吸收与毫微晶尺寸的关系,理论计算与实验结果基本符合。     

自混合干涉信号的位相调制

自混合干涉因其结构简单、紧凑、稳定且易准直等特点而被广泛应用于测量领域。从自混合干涉和电光晶体调制位相的基本原理出发,通过将电光晶体引入自混合干涉外腔调制,研究了自混合干涉测量中电光晶体的位相调制性能。实验证明,利用晶体的调制性能对自混合干涉信号进行位相调制,在很宽的频率范围内都能保证很高的调制精度,测量误差小,具有很好的应用前景。     

环形光束的非线性传输及聚焦特性研究

针对用于产生光镊的环形光束,利用分步傅里叶-贝塞尔变换算法,对二维环形超高斯光束的非线性传输及聚焦过程进行了数值模拟,给出了环形光束聚焦场附近的光强分布,并分析了非线性调制对聚焦性质(包括焦面中心光强、焦面光强的横向分布、轴上光强和光束质量)的影响.研究表明,从聚焦角度来看,非线性调制中的位相调制比振幅调制对环形光束聚焦性质的影响程度要大;从非线性传输角度来看,随着非线性介质长度的增加,位相调制和振幅调制对环形光束聚焦性质各有不同程度的加剧,其中非线性作用对振幅调制的影响要比位相调制明显.     

彩色全息显示中液晶空间光调制器位相调制偏差的矫正方法

采用三基色激光照明并结合时分复用或空间复用技术,可实现基于液晶空间光调制器(LC-SLM)的彩色全息显示.但由于在不同激光波长入射条件下LC-SLM的位相调制特性曲线不同,难以同时满足多波长入射条件下2π线性位相调制的要求,致使彩色全息再现结果受到共轭像和零级斑的干扰.针对该问题,本文通过实验测试获得LC-SLM在不同波长入射时的位相调制特性曲线,并分析了RGB激光器各分量的位相调制特性曲线非线性偏差和调制幅度偏差对多阶位相型傅里叶变换相息图再现效果的影响.根据"查表法"建立了各波长入射条件下满足2π线性位相调制的灰度映射关系,并对RGB分量相息图进行修正.通过对修正前后RGB分量相息图的数值模拟再现和光电再现实验与分析,结果表明:该方法有效地克服了LC-SLM位相调制特性曲线偏差的不利影响,从而改善了彩色全息显示中各分量相息图的再现质量.     

漂白银盐干板形成位相编码片的特性分析

本文讨论了银盐干板经过漂白而获得位相编码片的整个过程的传递特性,说明了编码片所具有的不同位相光栅结构,并计算了由此不同结构和光源色温所决定的色度曲线。分析了胶片的非线性效应对位相光栅调制深度及编码效果的影响。     

位相调制产生“热像”效应理论研究

通过理论分析和数值模拟方法，研究了高功率激光系统中的非线性“热像”效应. 利用菲涅耳-基尔霍夫衍射积分和非线性近轴波动方程，在远场近似及光学薄近似条件下，得出了位相调制产生“热像”出现的位置及强度满足的解析关系.结果表明，“热像”形成在非线性介质后与衍射物对称的位置，其强度可能比振幅调制产生“热像”的强度大几倍. 通过计算机模拟，并与理论预测结果进行比较，显示两者符合较好. 同时给“热像”的形成过程赋予了明确的物理意义，指出“热像”的形成类似于同轴位相夫琅禾费全息过程. 关键词： “热像”效应 全息成像 小尺度自聚焦 高功率激光     

索尼LCX029CRT液晶显示器纯位相调制特性的研究

为了研究索尼LCX029CRT液晶显示器纯位相调制特性,设计了索尼LCX029CRT液晶显示器的驱动电路,并搭建了测试光路对其纯位相调制特性进行了研究,同时对光路进行了理论分析。实验获得一组移动的干涉条纹,实验测试研究结果表明索尼LCX029CRT液晶显示器具有π／2的相位调制特性。     

索尼LCX029 CRT液晶显示器纯位相调制特性的研究

为了研究索尼LCX029CRT液晶显示器纯位相调制特性,设计了索尼LCX029CRT液晶显示器的驱动电路,并搭建了测试光路对其纯位相调制特性进行了研究,同时对光路进行了理论分析。实验获得一组移动的干涉条纹,实验测试研究结果表明索尼LCX029CRT液晶显示器具有π/2的相位调制特性。     

高功率激光光束经颗粒污染后的近场衍射效应

采用高功率激光驱动器设计软件Laser designer数值研究了激光光束经颗粒污染后的近场衍射特性. 对颗粒污染所产生的调制进行了分类, 并详细分析了真空和石英玻璃中, 振幅调制型和位相调制型颗粒污染对光束近场的影响. 研究结果表明, 无论在真空或石英玻璃中, 位相型颗粒污染对高功率激光光束的近场调制影响较大. 且在石英玻璃中, 位相型硬边颗粒污染所引起的高功率激光光束小尺度自聚焦热像调制现象相当严重. 而由颗粒污染引起光束强区的横向偏移, 却在一定程度对小尺度自聚焦有抑制作用.     

快速与慢速饱和吸收体被动锁模掺铒光纤激光器的理论分析

利用半导体饱和吸收波导作为慢速饱和吸收体与非线性快速饱和吸收体相结合，建立了共同被动锁模掺铒光纤激光器的理论模型-分析了半导体饱和吸收波导、光纤自相位调制和自振幅调制对锁模脉冲宽度和脉冲啁啾的影响- 关键词：     

强激光条件下5CB液晶中的激光诱导衍射环现象

强激光经5CB液晶传播时会产生非线性自相位调制现象,利用532 nm和1 064 nmCW激光研究了强激光条件下5CB液晶中的激光诱导衍射环现象,并对强激光在5CB液晶中产生自相位调制的现象和机理进行了讨论.当532 nm激光和1 064 nm激光功率密度分别大于10 kW/cm2和300 W/cm2时,接收白屏上有较明显的衍射环现象|当激光分别持续作用数十毫秒和数百毫秒量级时间时,接收屏上的衍射环现象消失.分别利用基尔霍夫衍射积分公式的菲涅耳近似和夫朗和费近似形式对5CB中激光自相位调制和激光诱导衍射环进行了数值模拟,数值结果与实验结果符合的较好.基于热传导理论定性分析了5CB液晶在不同波长和入射条件下的三阶非线性系数.结果表明：在强激光入射条件下,热效应是自相位调制的主要原因,这种三阶非线性系数除了与液晶的吸收系数和作用时间相关,还与激光作用面积甚至激光诱导指向矢转动过程相关.     

Compensation of self-phase modulation in fiber-based chirped-pulse amplification systems

We demonstrate a simple, all-fiber technique for removing nonlinear phase due to self-phase modulation in fiber-based chirped-pulse amplification (CPA) systems. Using a LiNbO3 electro-optic phase modulator to emulate a negative nonlinear index of refraction, we are able to remove 1.0 pi rad of self-phase modulation acquired by pulses during amplification and eliminate nearly all pulse distortion. Our technique is high speed, removes nonlinear phase on a pulse-to-pulse basis, and can be readily integrated into existing CPA systems.     

Spectral super-broadening of ultra-short pulses in a nonlinear kerr medium; Effect of relaxation

The combined influence of self-phase modulation, self-steepening and nonlinearity response time is modelled by a simple algorithm. Computer simulation of the supercontinuum spectrum generated by the three combined effects shows asymmetric Stokes-anti-Stokes broadening. The extents of these asymmetric Stokes-anti-Stokes sides are situated between those obtained by traditional self-phase modulation (SPM) and those obtained by combining SPM and self-steepening in the case of instantaneous nonlinear response.     

Generation of photon pairs in dispersion shift fibers through spontaneous four wave mixing: Influence of self-phase modulation

Correlated signal and idler photon pairs with small detuning in the telecom band can be generated through spontaneous four-wave mixing in dispersion shift fibers. However, photons originated from other nonlinear processes in optical fibers, such as Raman scattering and self-phase modulation, may contaminate the photon pairs. It has been proved that photons produced by Raman scattering are the background noise of photon pairs. Here we show that photons induced by self-phase modulation of pump pulses are another origin of background noise. After studying the dependence of self-phase modulation induced photons in signal and idler bands, we demonstrate that the quantum correlation of photon pairs can be degraded by the self-phase modulation effect. The investigations are useful for characterizing and optimizing an all fiber source of photon pairs.     

Thermal-induced nonlinear optical characteristics of ethanol solution doped with silver nanoparticles

The investigation of nonlinear optical characteristics of ethanol solution doped with is presented. A large thermal-induced third-order nonlinear refractive index up to silver nanoparticles 1.941× 10^-7 cm2/W is obtained from the mixed solution under 488-nm continue wave （CW） laser irradiation, which may result from surface plasmon resonance （SPR） enhancement effect of silver nanoparticles as well as high thermo-optic coefficient and low thermal conductivity of ethanol. Obvious spatial self-phase modulation and influence of thermal-induced negative lens effect are observed when a beam propagates through this solution, indicating promising applications such as optical limiting, beam flattening, and so on.     

Reversing intrachannel ghost-pulse generation by midspan self-phase modulation

Intrachannel pulse interactions are the dominating nonlinear effects in modern transmission systems with high modulation speeds. Scaled symmetries have proved to be effective in suppressing amplitude and timing jitter of mark pulses due to nonlinearity but not for ghost-pulse generation into the empty slots. A method of using midspan self-phase modulation to reverse the generation of ghost pulses due to intrachannel four-wave mixing is proposed. Computer simulations demonstrate significant improvement of signal quality by a combination of scaled symmetries and midspan self-phase modulation.     

Effect of multiphoton absorption and free carriers in slow-light photonic crystal waveguides

We examine the effects of multiphoton absorption, free carriers, and disorder-induced linear scattering in slow-light photonic crystal waveguides. We derive an analytic formulation for self-phase modulation including the group velocity scaling of the nonlinear phase shift in materials limited by three-photon absorption as a representative nonlinear process. We investigate the role of free carriers and derive an approximate critical intensity at which these effects begin to strongly modify the optical field. This critical intensity is employed to determine an optimal group index for the self-phase modulation in the slow-light devices. These observations are confirmed with numerical modeling.     

Transform-limited spectral compression by self-phase modulation of amplitude-shaped pulses with negative chirp

Spectral compression by self-phase modulation of amplitude- and phase-shaped pulses is demonstrated as superior compared to pulses that have only been phase shaped. We synthesize linearly negatively chirped parabolic pulses, which we send through a nonlinear photonic crystal fiber, in which self-phase modulation compresses the spectrum of the pulses to within 20% of the Fourier transform limit.     

Nonlinear refractive index measurements and self-action effects in Roselle-Hibiscus Sabdariffa solutions

We report the observation of self-action phenomena, such as self-focusing, self-defocusing, self-phase modulation and beam fanning in Roselle-Hibiscus Sabdariffa solutions. This material is found to be a new type of natural nonlinear media, and the nonlinear reflective index coefficient has been determined using a Z-scan technique and by measuring the critical power for the self-trapping effect. Z-scan measurements show that this material has a large negative nonlinear refractive index, n ₂ = 1 × 10^?4 esu. A comparison between the experimental n ₂ values and the calculated thermal value for n ₂ suggests that the major contribution to nonlinear response is of thermal origin.