Stimulated raman scattering in hydrogen

An experimental investigation to determine the threshold powers for stimulated Raman scattering in compressed hydrogen at room temperature will be presented. The pressure range of the hydrogen gas was from approximately 2 to 28 atm. Ruby laser light up to 120 MW was used as the incident beam. Both linearly and circularly polarized light were used. It was found that circularly polarized light could stimulate the rotational Raman, S₀(l), line as well as the vibrational Raman, Q₁(l), line while linearly polarized light could only give rise to the stimulated Q₁(1) line in the present power range. It was also found that the threshold power for the stimulated Q₁(1) line is higher for circularly polarized light than for linearly polarized light. The threshold power of the stimulated Q₁(1) line by linearly polarized light was found to depend on the gas density in general agreement with the theory. On the other hand, the threshold power of both stimulated S₀(1) and stimulated Q₁(1) lines by circularly polarized light agreed with theory only when the effect of a competing nonlinear process with a gain dependent on gas density was included