在LiNbO3∶Fe晶体中实验观察了由内在噪音引起的调制不稳定性和加入振幅掩模后产生的调制不稳定性,并对二者进行了比较。在使用振幅掩模时,根据晶体c轴方向与振幅掩模所带周期格子暗斑主轴方向的关系,分两种配置进行了观察比较,第一种配置是二者平行,第二种配置是二者成45°夹角。实验结果表明,掩模的加入加快了调制不稳定性的出现,但在第二种配置下产生的调制不稳定性对晶体内已形成的光子晶格的影响较小,并且这些周期性的光子晶格反过来对调制不稳定性的进一步发展有很好地抑制作用。由于光孤子有很高的应用价值,而调制不稳定性被看作是光孤子形成的预兆,所以研究它具有广泛的应用前景。

The modulation instability in two cases is experimentally observed in self-defocusing LiNbO3∶Fe crystal. One case is that the modulation instability is induced by intrinsic noise and another case is that the amplitude mask is joined in the experimental setup. Some comparisons between the two conditions are made. The amplitude mask used is with periodic lattices dark spot. When the amplitude mask is used,two configurations are observed according to the relationship of the c axis of the crystal and the principle axis of the periodic lattices dark spot. The first configuration is when they are parallel,and the second configuration is when the angle is 45°. The experimental results show that the participation of the mask accelerates the appearance of the modulation instability in the two configurations. But the modulation instability has a smaller effect to the formed photonic lattices in the crystal for the second configuration. And the photonic lattices have a strong suppression to the further development of the modulation instability conversely. Because the optical soliton has very high application value,and the modulation instability is seen as a precursor of the formation of the soliton,so the study of it has a widespread application prospect.