Laser Direct Writing Technology On Curved Surface

It is useful in many applications to fabricate large computer-generated diffractive optical elements (DOEs) on curved surfaces. The refractive/diffractive hybrid optical system is more simple, light, and compact. There are many applications for use in the measurement of convex secondary mirrors, ultraviolet spectroscopic instruments, armament, and space optical system.In this paper, series of work about the fabrication of large computer-generated diffractive optical elements on curved surfaces is carried out supported by the National Natural Science Foundation (60078006) and State Key Laboratory of Applied Optics of the Chinese Academy of Science.1. The exposure dose distribution and line width control for the laser direct writing system are analyzed. Some experiments are also carried out.2. We present a new method to correct the joint error of laser writer without the reduction of throughput. By digitization, we optimize the intensity data of the incidence beam at the vicinity of start point and end point.3. We obtained photoresist film with uniform thickness on the large concave substrate by selecting proper spin-coating parameters, which mainly involve spin rate, spin acceleration, and viscosity of the photoresist.4. We demonstrate experimentally the lithography technique to fabricate a large computer-generated diffractive optical element (DOE) pattern on a concave lens surface with precise alignment by using a laser direct writer.5. We demonstrate experimentally the technique to fabricate large DOEs in the thick film on a concave lens (mirrors) surface with precise alignment by using the strategy of exposure twice.6. We fabricated a large computer-generated holography on a concave lens surface to test the convex secondary mirrors surface.At the end of this paper, the prospect of this work and technique is given.