声表面波在声栅上的Bragg衍射

本工作揭示了声表面波在声栅上的Bragg型衍射效应。应用简正波理论近似处理了在强Bragg条件下,声表面波在声栅上衍射的一些规律:栅阵内简正模式,偏转角和偏转效率与入射声波工作频率和声栅参数的关系。实验上,我们在y切割LiNbO₃压电晶体表面,用金属栅阵构成声栅,用光学法观察了声表面波(Rayleigh波)在上述声栅上的Bragg型衍射现象,并测量了偏转角和偏转效率随工作频率的关系。实验与理论结果比较表明,二者基本上是符合的。 关键词：

ON THE BRAGG-DIFFRACTION OF SURFACE ACOUSTIC WAVES BY ACOUSTIC GRATING

The surface acoustic wave diffraction phenomena on acoustic gratings in Bragg regime have been explored.The modal approach has been used to treat this problem under strong Bragg condition. Some results, including the eigen-modes in the grating, the equation of the deflected angles, and the analytical expression of deflection efficiency which depends on the operation frequency and the grating parameters, have been obtained.Experimentally, the image of the diffraction acoustic fields on acoustic grating which was composed of some aluminium film stripes on y-cut LiNbO₃ crystals have been visualized by means of Schlieren method. Some excellent photographs of diffraction fields have been obtained, and the deflection angles and deflection efficiency at different frequency have been measured by using optical method. The comparison between the theoretical and the experimental results shows that the agreement is satisfactory.