Investigation of the optical limiting properties of acid blue29 in various solvents

The optical limiting properties of acid blue29 solutions in different solvents are investigated. Experiments are performed using a CW He-Ne Laser beam at 632.8 nm wavelength and 35 mW power. The strength of the optical limiting action is dramatically influenced by the solvent. Multiple diffraction rings were observed when the samples were exposed to laser radiation. The effect of concentration, solvent and laser intensity on the diffraction rings are studied experimentally. Our results show that the nonlinear refraction is the dominant mechanism to explain the optical limiting behavior in acid blue29.     

Calculation of the gain in optically active photorefractive crystals considering the self-diffraction in a two-wave mixing process

We present a physical and computational procedure to calculate the gain in a two-wave mixing process in a thick optically active photorefractive BSO crystal under diffusion regime. The procedure is based on the integration of the amplitude of the signal beam through the sample. In the model, the effects of self-diffraction are taken into account by using the more general expression of the diffraction efficiency for the case of dynamic gratings. It allows also including the effects of the optical activity on the coupling factors and not only on the rotation of the optical field vectors when the waves are propagated along the crystal. The <001> crystallographic configuration is used. The model is used to predict the behavior of the gain as a function of the beam polarization angle. Numerical and experimental results using crystals with thickness of 5 mm and 10 mm are presented. A good agreement between the proposed model and the experimental measurements is observed.     

聚对苯撑乙烯衍生物/氯仿溶液的自衍射及光限幅特性的研究

用532 nm基模高斯光束对2-甲氧基5-丁氧基取代聚对苯撑乙烯的氯仿溶液进行激光诱导衍射实验及光限幅特性的研究.实验发现,当高斯光束通过样品溶液时,在远场处出现衍射环;随着入射功率的增大,衍射图案会发生显著的变化.理论分析表明,该现象可以用光克尔效应、热效应作用下的附加相位孔对入射光束的衍射行为来解释.还进一步研究了532 nm激光作用下样品溶液的光限幅特性,根据实验结果分析得出:由热效应引起的自衍射是产生光限幅特性的主要机制.     

The dynamic characteristics of self-diffraction efficiency of azo polymer film

When two coherent beams illuminate into the azo-dye-doped polymer film with small angle and equal intensity, the phenomena of self-diffraction occur. We study the dynamic characteristic of self-diffraction efficiency experimentally and theoretically by the model of population grating, which is formed by the molecules populations of trans and cis state modulated by the coherence optical field.     

利用偏振光控制的光学转换新方法

报道了一种新的非相干-相干光学转换方法,该方法利用了偏振光对含偶氮材料中自衍射的增强和抑制作用,所用样品为具有较大光致双折射(δ_n=1.3×10^-2)的偶氮掺杂聚合物薄膜.研究结果表明,当泵浦光偏振方向与两束记录光垂直/平行时,衍射效率得到了极大的增强/抑制.本文通过改变泵浦光的偏振方向得到了入射非相干图象的正片和负片.     

细菌视紫红质的自衍射效率与最佳入射角研究

研究了弱光强下细菌视紫红质膜(bR膜)的自衍射特性.给出了弱光强下相干光在bR膜中产生的振幅光栅光强分布模型,并用ysinαx近似表示透射光强分布,结果与实验吻合.给出了不同透射光强y与指数α的对应关系.结果表明,在bR膜及入射光波波长给定的情况下,入射光强越小,对应的α值越大,当入射光强为0.072/T(mW/cm2)时,α等于1.计算出不同入射光强和入射角下的自衍射效率.结果发现,对应于最大衍射效率的最佳入射角为2°.