基于衍射条纹非对称性的表面波衰减系数的测量

Measurement of the attenuation coefficient of surface acoustic wave by phenomena of the asymmetry of diffraction patterns

通过采用将入射光掠入射到频率为几百赫兹的衰减低频液体表面波上,观察到了清晰的间距分布具有明显非对称性的衍射条纹。当入射光掠入射到低频液体表面上时,衍射图样非对称分布具有普遍性。理论上得到了考虑表面波衰减影响后观察屏处衍射光强分布的解析表达式。理论结果表明:衍射图样的这种非对称分布与衍射级次、入射光波波长、液体表面波波长及表面波衰减系数有关;正负级次衍射亮条纹距离中央零级亮条纹的间距体现表面波衰减信息;正衍射级次之间以及负衍射级次之间的条纹间距体现表面波波长信息。利用所提出的方法实现了对几百赫兹液体表面波的衰减系数的实时便捷测量。

Light diffraction from liquid surface acoustic waves at low frequency is experimentally realized. In the experiment steady and visible diffraction patterns are obtained and the obvious asymmetry of patterns is observed. The theoretical analysis based on asymmetry diffraction fringes provides a closed-form solution for the intensity of light distributed on far-fields. It indicates that the space between positive-order and zero-order or the space between negative-order and zero-order includes the attenuation information. This new technique is used to determine the attenuation coefficient of the surface wave at these frequencies in real time.