Pumping with diodes

The development of semiconductor lasers for pumping solid-state laser crystals is discussed. The basic operating principles of solid-state devices are reviewed to show why this new development is so important. Among the first of the new diode-laser technologies to be applied to pumping was the phase-locked array, which produced much higher power outputs and higher brightness from room-temperature CW diode-laser systems. With diode-laser arrays capable of power outputs between 0.2 and 2 W, and relatively good beam quality, it became possible to pump Nd:YAG and other crystals longitudinally, with the pump and laser output beams either parallel or antiparallel in the laser crystal. Diode pumping allows the flowing cooling liquids and fluctuating arc lamps used in conventional lamp-pumped lasers to be replaced by solid heat sinks and stabilized pump lasers. As a result, designers can build low-power solid-state lasers having high mechanical and thermal stability. Short-term linewidths in the kilohertz range can be obtained from diode-pumped devices, and the long-term drift of monolithic devices can be kept within 50 MHz for over an hour (for a center frequency of 3*10/sup 8/ MHz) by controlling the laser-crystal temperature.<>