Space Optical Communications, High-precision Laser Beam Collimation System Design

With the rapid development of communication technology in recent ten years, space optical communication has become a communication way with a wide application prospect. However, laser collimation system, which can exert great influence on communication effect and transmission distance, plays a significant role in optical communication system.In this thesis, the technology of high precision laser beam collimation, which is one of the key techniques in space optical communication, has been deeply researched and the collimation optical system has been designed.The main contents involved in this dissertation are as follows:1. Based on studying the Gaussian beam's change law through a single thick lens by applying the approach of system transfer matrix and ABCD law , the formulae of far filed divergence angle of Gaussian beam passing through a telescope system has given in this paper. Besides, the influence of structure parameters to the collimation are analyzed .The analysis showed that with an appropriate adjustment of structure parameters, the collimation effect can be effectively improved.2. Designed a telescope collimation system by computer simulation, and optimized system aberration with optical software ZEMAX. Simulation results indicate that the designed system has a good collimation effect, which can compress the divergence angle into 0.5mrad.3.According to geometric optical principle, semiconductor laser beam collimation system has been optimized and designed. In the situation of ignoring the inherent astigmatism of semiconductor laser, an optical system including an aspheric lens and a pair of prisms has been designed to collimate the elliptical semiconductor laser beam. When the inherent astigmatism has been taken into account, an optical system comprising tow aspheric cylindrical lenses has been calculated and designed.4.Based on refraction law in vector form as well as the ray-tracing method, the system parameters are calculated and optimized via computer simulation. On the basis of simulation results, we draw a conclusion as follows: Without considering the inherent astigmatism, any spatial ray can be collimated ideally by the system including a aspheric lens and a prisms in theory. When the inherent astigmatism has been taken into account, the light rays either in the perpendicular transverse direction or in the parallel transverse direction can be perfect collimated by the tow cylindrical lenses system theoretically. Simulation results also showed that the two systems mentioned above both can circularize the highly divergent elliptical beam has been into a 2cm spot at the output of the optical system.