可见光下3维针孔的衍射波面分析

针孔是相移点衍射干涉仪中的关键元件。为了探究针孔的尺寸、制造针孔的材料以及材料的厚度对衍射波面质量的影响,确定点衍射干涉仪的测量精度,采用时域有限差分法分析获得了近场数据,并利用瑞利-索末菲矢量衍射理论将近场数据外推得到远场数据,通过远场处理数据分别对TM和TE偏振光入射针孔时,针孔的大小、材料以及材料厚度对衍射波波面质量的影响进行了理论分析和仿真模拟,得到了相应变化曲线图。结果表明,若要获得理想的球面波,材料厚度不能低于300nm,适当的孔径尺寸可以降低衍射波面误差;当孔径为300nm左右时,波面的均方根误差可达到λ/1000(λ=632.8nm)。这一结果对相移点衍射干涉仪的设计和应用是有帮助的。

Analysis of diffractive wave-front of 3-D pinhole under visible light

A pinhole is one of the key components in a phase-shifting point diffraction interferometer (PS-PDI). In order to study the effect of the size of pinhole, material of pinhole and thickness of material on the quality of diffraction wave-front, and determine the measurement accuracy of the PS-PDI, near-field data was obtained by means of the finite-difference time-domain method, and then the data of far field based on Rayleigh-Sommerfeld vector diffraction theory could be acquired from near field data. The quality of diffractive wave-front was analyzed under the uniform incident light with TE and TM polarization, and the corresponding curve was achieved. The results show that in order to obtain perfect wave-front, the thickness of material should not be less than 300nm. Appropriate aperture size can reduce the error of wave-front. When the size of pinhole is 300nm, the root mean square wave-front error is below λ/1000(λ＝632.8nm). It is of great help to design and application of a PS-PDI.