Optimization of a Raman shifted dye laser system for DIAL applications

We describe an efficient Raman shifted dye laser system that generates tunable radiation at 765 and 940 nm with a bandwidth of 0.03 cm(-1). Operating a Raman cell at hydrogen pressure below 14 atm, we recorded optimum first Stokes energy conversions of 45% and of 37% at 765 and 940 nm, respectively. Optical depth measurements made at the centers of twenty-five absorption lines in the P branch of the oxygen A band imply a high spectral purity for both the laser and the Raman shifted radiation, and thus indicate the feasibility of using the stimulated Raman scattered radiation for differential absorption lidar (DIAL) measurements.