低频液体表面波衍射条纹的不对称性

为了对低频液体表面波衍射条纹强度及位置进行分析,用低频信号发生器驱动振子,产生稳定的液体表面波,一束激光照射液面,表面波对光形成了位相型光栅,产生了清晰的衍射图样.过中心沿水平方向对衍射图样进行线性扫描,得到了衍射条纹强度随位置的变化曲线及各级衍射条纹的中心位置及强度值,发现了衍射条纹强度及位置具有明显的不对称分布.理论上给出了衍射条纹强度与表面波之间的关系,并且对衍射条纹位置的近似条件及半角宽度进行分析,分别解释了在斜入射的情况下衍射条纹位置及强度的不对称分布.理论上推导出在垂直入射的情况下,衍射条纹的位置及强度是对称分布的.理论与实验结果比较吻合.

The asymmetry of intensity and position of diffraction patterns

In order to analyze the intensity and position of the diffraction pattern from the liquid surface wave,a low-frequency signal generator was used to produce a sinusoidal output at low frequency,which was then used to drive the surface acoustic wave(SAW)exciter.A laser beam was directly incident upon the water surface where the SAW was excited and diffracted.Thus,a technique for low-frequency SAW visualization was developed based on the light diffration.The intensity curve was draun and the intensity and position of each-order diffraction spots were obtained.The asymmetrical position and intensity were also discovered.The dependence of the diffraction intensity on the liquid surface waves was theoretically derived.The approximate conditions of the surface wave diffraction and the half angular width were analyzed,respectively.When laser was at normal incidence,the symmetrical distribution was theoretically derived.The theoretical and experimental results are in good agreement.