Precise alignment of hybrid refractive-diffractive elements based on Fizeau interferometer

Abstract

In the process of fabrication and assembly of hybrid diffractive-refractive optical systems, the quality and performance of the hybrid devices significantly depend on the alignment level of elements. But for the inherent magnificent difference existed between traditional and diffractive elements, the conventional alignment method does not fit to be used in the hybrid optical system, so alignment error, a widely existed and difficult to be solved problem, has been the main bottleneck which seriously blocks the development of the application of the hybrid optical systems, and how to simply achieve the precise alignment of the diffractive and refractive elements of a hybrid device is an urgent problem needed to be solved by the researchers in this field. This paper presents that using Fizeau interferometer to simply align a plano-convex refractive element with a diffractive element with high precision. The theory of the method is analyzed and its precision is also estimated, and it is clearly shown that a system aligned by this method can meet the demand of optical systems, and the experimental results are satisfactory. All these show that the simple method presented in the paper is feasible and effective, and can constructively guide and enlighten people to solve other problems related to alignment error encountered in most necessary steps during the process of realizing a practical hybrid optical system.