1-3 Micron Tunable Diode Pumped Solid State Laser Sources

High pulse energy, high repetition rate, tunable, narrowband sources are needed for optical pumping of mid-infrared gas laser converters. The source needs continuous tunability over the 1-3 micron band to access different overtone bands in various gaseous gain media. Due to the need for diode pumping of the source, efficiency is critical to minimizing diode costs. Our approach is efficient generation of the 1-3 micron output with an injection-seeded optical parametric oscillator-optical parametric amplifier (OPO/OPA) system. The pump beam for the OPO/OPA system is the fundamental or second harmonic of a Hd:YAG laser. The key innovation is dramatic enhancement of the conversion efficiency in the OPA by resonantly feeding back the unconverted pump beam. Pump feedback is accomplished with a resonant ring cavity built around the OPA. Theoretical OPO conversion efficiencies (pump to signal + idler) are near 30% without feedback, and between 75-80% with feedback. System efficiency is examined further through a preliminary design study on the diode-pumped drive laser. Alternative materials such as Yb:YAG are more effective storage media than Nd:YAG> thus, there is tremendous potential for reducing the diode laser requirement, and thus the cost. The Phase I objectives are to demonstrate efficient conversion in a pump feedback OPA through experimental and analytical efforts, and define the architecture of the diode-pumped drive laser. In Phase II, the drive laser, seeded OPO and OPA are further developed and integrated into a single tunable system to be delivered to the Air Force at the end of Phase II.