可调相位型液体表面波衍射光栅效应的研究

Study about tunable phase modulation gratings by means of liquid surface wave

为了研究可调相位型液体表面波光栅的衍射效应,采用低频信号发生器驱动振子、激发产生液体表面波的实验方法,得到了清晰、稳定的衍射图样,观察到衍射条纹间距随着液体表面波频率的改变而改变。并且在特定频率输出条件下,改变表面波振幅,可以得到衍射条纹的缺级现象。根据物理光学理论,周期性振动的表面波可以视作为一相位型光栅,对入射光进行相位调制的理论模型,理论上得出了衍射条纹的强度分布与表面波振幅之间的解析表达式,很好地解释了条纹间距变化和缺级现象,和实验符合较好,并且与普通刻痕光栅的光衍射现象进行了对比分析。结果表明,二者虽然表象类似,但物理机理却有很大差异。由于液体表面波的参量具有可调性,因此其衍射效应明显,可用于教学和科研。

In order to study the diffraction effect of the tunable phase modulation grating, steady and explicit diffraction patterns were obtained with the low-frequency generator driving the exciter to generate the low-frequency liquid surface wave （LFLSW）. The distance between the diffraction patterns was variable with the frequency of the surface wave. Furthermore, the diffraction order might disappear at certain amplitude of the LELSW. According to the physical optics theory＇, the periodical modulated LSW can be regarded as a phase modulated grating. The corresponding analytic expression of intensity distribution of diffraction patterns was derived, which explained the experimental phenomenon well. And the diffracted effect of the LSW was compared with that of the plane scotch grating. The results show that the LSW gives better diffracted effect.