Continuous wave Raman laser in H/sub 2/

Abstract

Summary form only given. With the advent of the new technology of high-finesse cavities, it now becomes possible to use these high-finesse cavities to build a widely tunable cw Raman laser that can be pumped with lasers at the milliwatt level. The apparatus used to make the first cw Raman laser in H/sub 2/ is shown. For this experiment, we chose to use a cw Nd:YAG laser with output powers up to 200 mW. The output of this frequency-doubled Nd:YAG laser at 532 nm was sent through a Faraday isolator to minimize feedback to the Nd:YAG laser. An electro-optic modulator was used to place sidebands on the carrier frequency required for locking the pump to the cavity. The laser beam traveled though a two-element lens pair used to mode match the pump beam to the cavity. A polarizing beam splitter cube in conjunction with a quarter-wave plate allowed for monitoring of the beam reflected from the cavity. Using a narrow-band filter, a fast detector was then used to measure the error signal. The error signal entered the servo, and the slow corrections were sent to the cavity piezo, while the fast corrections were sent to the laser. The output of the cw Raman laser was measured at the exit of the cavity. By adjusting the locking servo, the pump laser could be locked to the side of the cavity line, resulting in a variable pump power in the cavity. As the pump was moved across the cavity resonance, the average pump and Stokes powers were measured. The laser exhibits a typical laser power versus pump power curve, with a threshold at /spl sim/50 mW. The Raman laser has a maximum output of 1 mW, which corresponds to a photon conversion efficiency of /spl sim/2%. The measured power slope efficiency is at 7.1%. With future design changes in the cleanliness of gas handling systems, we expect the threshold to lower to the milliwatt level and the conversion efficiency to approach 50%.