高灵敏度的多波长多光束干涉仪

作者用多纵模He-Ne激光照明多光束Fabry-Perot或Fizeau干涉仪,在一个自由光谱范围内,形成与不同波长对应的子条纹,相邻条纹间的间隔代表的波长数依赖于He-Ne激光腔的光学长度npL与F-P腔长nd之比r=nd/npL.当r是整数时,不同波长对应的相邻干涉级次相互重叠,条纹间隔为λ/2且强度最大;当r是分数时,r=N/M,N,M为互质的整数,相邻条纹之间间隔为λ/2M.不难做到M=10,条纹间隔为K/20.由于多光束干涉条纹细而锐,有利于读数精度提高,可以测量λ/500的程差变化,不需内插就可以给出空间分布的足够信息.这对光学元件的高精度面形检验及低密度流场显示有实际的应用前景.给出了应用的若干例子.

High sensitivity multiple beam interferometry

It is shown that a Fabry Perot-interferometer with small wedge angle or a Fizeau interferometer is illuminated by a collimated multiple longitudinal mode He-Ne laser beam,the spacing of adjacent fringes depends on the ratio r=d/L ,here d and L are the length of the interferometer and laser cavity.When r is a integral,the different order fringes corresponding to different modes are overlapped and the intensity of fringe is maximum and the fringe spacing represents λ/2.When r is fraction,r=N/M,N and M are both prime numbers,the fringe spacing is corresponding to λ/M.It is easy to get M= 10 for a long cavity He-Ne laser,the interferometric sensitivity is then 10 times that of M-Z interferometer.This interferometer can be applied to examining of the optical components with high precision and the measurement of low flow field.Some applications are presented in this paper.