白光和激光产生的调制不稳定性的比较

Comparison of the modulation instability induced by the white light and the laser

在非线性自散焦LiNbO_3∶Fe晶体中,实验观察了用激光作光源和用白光作光源两种情况下所产生的调制不稳定性,并从三个方面对这两种情况进行了比较。实验结果表明:在两种情况下,达到稳定状态前,MI现象都会随辐照时间的增加而变得越来越清晰,并且MI图样都会随着入射光束形状的变化而变化。不同的是,用白光作光源时,灯丝长度方向与晶体c轴方向的夹角大于等于45°时出现MI,而用激光作光源时,入射光束方向与c轴方向的夹角不大于45°才出现MI。

The modulation instability caused by laser light source and white light source is respectively observed experimentally in nonlinear self-defocusing LiNbO_3∶Fe crystal.And some comparisons are made from three aspects.Experimental results show that in the two cases,MI phenomenon becomes more and clearer with the increase of irradiation time before reaching the steady state,and MI pattern changes with the shape of the incident beam.When the white light is used as the light source,MI begins to appear when the angle between filament direction and the crystal c axis is great than or equal to 45°;when the laser is used as light source,MI begins to appear when the angle between the direction of the incident beam and the c axis is not greater than 45°.