本文报道一种新型的光敏蛋白——细菌视紫红质LB膜,它的饱和吸收强度为0.42 W/cm2,饱和非线性折射率高达5×10-2 cm2/W,非线性响应的特征时间在ms量级,我们首次在这种材料中采用简并双光束相互作用方法观察其中感应的吸收体布居光栅所产生的高次衍射,并根据简化的bR分子光循环模型(bR(570)与M(410),导出了高次衍射光强度和入射光强度之间的关系,从而进一步求得这种材料的饱和吸收强度和非线性折射率等参量。

We report a new kind of biomolecular LB films composed of a photosensitive protein-bacteriorhodopsin. The saturated absorption intensity and nonlinear refractive index of the material are estimated to be 0. 42 W/cm2and 5×10-22cm2/W and the typical response time of the nonlinearities is about 1ms. High to third-order self-diffractions by population gratings in the LB films have been observed in the degenerate two- beam interaction experiment. The relation between intensity of each order diffracted beam upon the total incident intensity is deduced based on a simplified photocircle model of bacteriorhodopsin. The saturated absorption intensity and nonlinear refractive index of the material are then calculated by fitting the experimental data with the theoritical formuls.