High-repetition rate, short-pulse, diode-pumped solid state laser for space communications

The CNES (Centre National d'Etudes Spatiales) established the laser system characteristics for Mars-Earth spatial communications using the Pulse Position Modulation (PPM) technique. Today, diode-pumped solid-state lasers are under intense research and development. Indeed, in comparison with flash-lamp pumped laser, they offer significant advantages in terms of efficiency, compactness, lifetime and high beam quality. We have demonstrated that gain- switch operation is preferable to Q-switching technique to control and to obtain a good pulse width and amplitude reproducibility. The pulse width requirement and the laser-diode pumping scheme lead to a preferred configuration based on a microchip laser oscillator coupled to an amplifier. Experiments were performed with several microchips of Nd:YAG and Nd:YVO4 crystals pumped by fiber-coupled laser-diode. The design of the transversally-pumped amplifier is based on a modified multipass 1:1 confocally reimaging longitudinally-pumped amplifier proposed by Plaessmann et al.