Far field beam pattern of one MW combined beam of laser diode array amplifiers for space power transmission

The far-field beam pattern and the power-collection efficiency are calculated for a multistage laser-diode-array amplifier consisting of about 200000 5 W laser diode arrays with random distributions of phase and orientation errors and random diode failures. From the numerical calculation it is found that the far-field beam pattern is little affected by random failures of up to 20% of the laser diodes with reference of 80% receiving efficiency in the center spot. The random differences in phases among laser diodes due to probable manufacturing errors is allowed to about 0.2 times the wavelength. The maximum allowable orientation error is about 20% of the diffraction angle of a single laser diode aperture (~1 cm). The preliminary results indicate that the amplifier could be used for space beam-power transmission with an efficiency of about 80% for a moderate-size (3-m-diameter) receiver placed at a distance of less than 50000 km