Study on focusing performance of the twice reflecting laser focusing system

Laser thrusters characterized by feasible application perspective all possess the twice reflecting laser focusing system. Nonetheless, studies on its focusing performance are imperative for the research of flight route of the thruster and haven't been developed yet. Under three different focusing design modes, assisted with optical design software ZEMAX which employing Monte Carlo ray tracing, performance of twice reflecting laser focusing system including focusing performance parameters, radiation intensity distribution and the details of ignition region on the focusing plane are studied comparatively, and the studied two main angular aberrations are beam out-coming aberration from laser source and flying aberration from thruster itself. Studies show even slight aberration will result in steep falling focusing performance and strong deviation of beam spot for any focusing design mode, while different aberrations bring in distinctive falling tendencies and the evolutions of ignition region. It strongly demands the directional precision of laser beam, and the attitude control of laser thruster is indispensable. And it's not recommended that one focusing design mode is superior to another. Which kind of aberration is dominant should be taken into account when choosing focusing mode.