低频液体表面波激光衍射条纹的特征

Characters of Laser Diffraction Fringes from Liquid Surface Waves at Low-frequency

用激光衍射法实现了低频液体表面波稳定、清晰、反衬度非常高的条纹,并发现了缺级现象.理论上分析了表面波的光衍射效应,得到了衍射光场和表面波之间的解析表达式,表达式包括衍射因子和干涉因子.通过对衍射因子和干涉因子的分析,得到衍射条纹空间分布与表面波波长的关系、条纹的半角宽度与入射激光光斑覆盖表面波的个数和入射方向的关系、衍射光强度与表面波振幅的关系,并解释了条纹缺级现象.

High visible stationary laser diffraction patterns from liquid surface waves at low-frequency were obtained experimentally, and the disappearance of diffraction fringe was also observed. The dependence of the diffracted field upon the surface waves was derived by theory of wave optics. Based on the relations of the diffraction field and the surface wave, which conclude diffraction factor and interference factor, some relations were conformed such as： the diffraction fringes spatial distribution versus surface wavelength, the fringes half angular width versus the numbers of surface wave covered by laser spots and incidence angle, diffraction intensity versus surface wave amplitude. The disappearance of diffraction fringe was explained successfully.