对PPV衍生物非线性折射率的测量

利用532nm的连续激光对烷氧基非对称聚对苯撑乙烯衍生物的氯仿溶液进行诱导衍射实验,通过观察衍射环的个数可以估算出材料的克尔常数及非线性折射率。实验发现,当入射激光功率达到阈值0.77mW而小于3.36mW时,通过在接收屏处观察光克尔效应对激光横截面上的空间自相位调制而产生的衍射环个数,可以估算出样品溶液的克尔常数γ的大小近似为5.55×10-10m2/W及非线性折射率n2的大小为9.21×10-4esu。当入射激光功率继续增大时,由于热效应对激光横截面上的空间自相位调制产生的衍射环逐步淹没光克尔效应引起的衍射环,接收屏上的衍射图案将发生显著的变化。

Measurement of nonliear refractive index in PPV derivative/chloroform solution

The experiment of the laser-induced diffraction in poly-phenylene vinylene(PPV) derivative/chloroform solution is made by using the 532nm continuous laser.According to the number of the diffraction rings,the Kerr constant and nonlinear refractive index of the material can be estimated.It is found that:when input-power reaches the threshold 0.77mW but less than 3.36mW,it is mainly Kerr effect that causes the diffraction rings owing to spatial self-phase modulation while the Gaussian beam passing through the nonlinear medium.Therefore,the Kerr constant γ of PPV/chloroform solution (absorption cofficient 4.76cm^-1 at 532nm) is about 5.55×10^-10m²/W and the nonlinear refractive index n₂ is probably 9.21×10^-4esu.But as input-power is increased,diffraction rings caused by thermo-optic effect submerge diffraction rings caused by Kerr effect.