各向同性介质中任意偏振光的简并四波混频

在各向同性介质的简并四波混频中,就共线(探测光波矢平行于泵浦光的波矢)和非共线装置,线偏振和圆偏振等情况,推导出反射波的复振幅(包括偏振)与探测光和泵浦光的振幅、偏振、介质的三阶非线性张量元之间的关系式。在非共线装置中,泵浦光为平行的线偏振光时,可利用探测波与反射波的偏振方向间的关系求出x₁₁₁₁与x₁₂₂₁的比值;泵浦光为同旋性的圆偏振光时,可获得理想的复共轭波。在共线装置中,在反射波中总含有一定的非共扼的成分,振幅反射系数与样品厚度的关系可能是正切、双曲正切或线性函数关系;泵浦光为平行的线偏振光时,若|x₁₂₂₁|>|x₁₁₂₂|,可产生自振荡现象;在泵浦光为旋性相反的圆偏振光时,对圆偏振的探测光可产生理想的平面镜反射的效果,等等。结果可用来解释一些已知的实验结果,并对新的实验设计具有一定的指导作用。 关键词：

THE DEGENERATE FOUR-WAVE MIXING OF LIGHT WITH ARBITRARY POLARIZATIONS IN ISOTROPIC MEDIUM

The functional relations have been presented between the complex amplitude (including polarization) of reflected wave on the one hand and amplitudes, polarizations of pump and probe waves, the third-order nonlinear susceptibility on the other hand, for degenerate four-wave mixing (DFWM) in isotropic medium, in which the polarizations are linear and/or circular, and the geometry is collinear or non-collinear. In the non-collinear geometry, when the polarizations of pump waves are parallel to each other, one can determine the ratio x₁₁₁₁/x₁₂₂₁ from the angles between polarization directions of probe and reflected waves; when the polarizations of pump are circular polarizations of the same handedness, one can get the ideal complex conjugate wave in this geometry. In the collinear geometry, there are always some non-conjugate component in the reflected wave, and the functional relation between reflection coefficient of amplitude and the thickness of sample can have the form of tangent function, hyperbolic tangent function and linear function; when the polarizations of pump waves are parallel to each other and |x₁₂₂₁|> |x₁₁₂₂|, this geometry is capable of generating self-oscillation; when polarizations of pump are circular ones of different handedness, DFWM acts as an ideal plane-mirror for probe wave with circular polarization, etc. The results can be used to explain some well-known experimental results and provide some theoretical guidance for designing new experiments.