Space Optical Communication Semiconductor Laser Beam Collimation And Small-angle Measurements

Spatial laser communications is a new technology, which has got rapid development with specialist many years research. Laser communications has many advantages such as high-data-rate, high-bandwidth, significant cost savings, small size, light weight, low power attenuation. Beam control is one of the key techniques of laser communications, among which the divergence collimation and measurement are requirement for farther laser beam shaping. The aberrations of lens influence beam quality, the more big of the aberrations, the more bad of the beam quality. In this paper, we use Turbo C simulating the different aberration of different form lens, and get that the plano-convex lens can effectively reduce the spherical aberrations. According to the gassian character of the semiconductor laser, the transform of laser beam through lens is discussed and the relationship of the divergence angle and lens parameter is got. We use the Matlab software demonstrating the plano-convex lens can contract divergence angle commendably. Optical antenna can ulteriorly reduce laser divergence collimated. Transmission and reflecting optical antennas are analyzed and compared, and the collimation theory and design request of the cassegrainian telescope, using in spatial laser communications, are discussed concretely. Different measurement methods of divergence are introduced domestic and abroad, and their advantages and disadvantages are stated. In terms of the lens transform matrix and the definition of the divergence angle, the far field facula method is validated. After the laboratorial system is set up, the divergence angle is measured practically using the beam profiler diagnostic instrument and the measurement errors are analyzed. Looking on the gassian beam as geometrical ray, the divergence angle is also measured in the lab by charge coupled device. Comparing the two kind of experiment results, it made clear that the divergence of the light source is milli-radian and can reach the request of spatial laser communications after being collimated by the optical antenna.