High-Power Diode Laser Transmitter for Aerosol LIDAR and Laser Ranging

The next generation of space-based instruments for NASA will be smaller and more efficient than ever before. In keeping with this requirement, LIDAR and laser ranging systems are being developed which are based on AlGaAs semiconductor laser diodes [1, 2]. These systems use pseudo-random noise (PN) intensity modulation of the laser in conjunction with a correlation receiver to improve the overall system sensitivity and allow the inherently low-power diode laser to compete with much higher power solid state and gas lasers. While the size and efficiency of diode lasers make them attractive for such applications, the high-power, quasi-CW intensity modulation of these devices can introduce deleterious effects, such as spectral linewidth broadening. In addition, the highly-divergent beams from diode lasers require fast (F/1) optical systems, which in turn place micron-level tolerances on their opto-mechanical alignment and packaging. We present here the design and performance of a high-power diode laser transmitter which addresses the problem of spectral broadening under large-signal intensity modulation and also the problem of micron-level tolerance opto-mechanical packaging. The laser transmitter is a candidate for an aerosol LIDAR system currently operating at the South Pole, and may also enable future NASA laser ranging and communication systems.