Analytic treatment of beam quality and power efficiency in a high-power transverse flow diode pumped alkali laser

Abstract

The performance of a 100 kW Rb–He diode pumped alkali laser system is predicted, including power scaling, optical efficiency, and beam quality. A transverse flow geometry with longitudinal diode pumping produces a nonlinear temperature profile in the flow direction, with temperature increasing by 124 K for a 0.5 m/s flow rate and a 30 kW/cm2 pump intensity. The optical-to-optical efficiency is 70%, and the tilt-corrected Strehl is 0.545 for this slow flow, 45 ms residence time design. By increasing the flow speed to 15 m/s (1.5 ms residence time), the efficiency is improved to 82%, and the laminar flow beam quality is near the diffraction limit, Strehl>0.99. Beam quality is adversely affected at higher helium pressure for the slow flow conditions.