Regenerative Raman amplifier utilizing rotational transitions in orthohydrogen

A regenerative Raman amplifier utilizing rotational transitions in the orthohydrogen molecule was constructed and investigated. Pumping was provided by Nd laser radiation (1.06 μ) with and without a light pipe. Injection of an external Stokes signal (1.13 μ) into the amplifier resonator made it possible to suppress lasing at the frequency of the first Stokes component, which appeared as a result of scattering by the vibrational levels of the orthohydrogen molecule. The efficiency of conversion of the pump energy into the first Stokes component was 15% in the absence of the light pipe and 25% in the presence of the pipe; the corresponding values of the power conversion efficiency were 60 and 50%, respectively.