Generation of tunable infrared radiation by stimulated Raman scattering on hydrogen in a prism–lens optical delay line

The threshold of stimulated Raman scattering was lowered by filling an optical delay line with hydrogen. Pumping was by a tunable neodymium laser. Lens–prism combinations were used as phase correctors in the delay line. The dependences of the energy of the Stokes component on the pump energy determined experimentally for different numbers of transits through the delay line were compared with the results of a calculation allowing for the losses in the components of this line. When the frequency conversion was by a factor of at least 2 and the tuning range was wide (tens of percent), the optimal performance was obtained from the optical delay line when total-internal-reflection prisms and lenses were combined in a single component and oriented at the Brewster angle.