Abstract

Liquid nitrogen (LN) is an ideal active medium for Raman shifters. Its high Raman gain gives rise to a relatively low threshold for stimulated Raman scattering (SRS), whereas thresholds for competing stimulated processes are considerably higher. The SRS in LN undergoes a parametric instability at high intensities. This is of practical importance since it offers the possibility of achieving photon conversion efficiencies approaching 100 % in an active region only ~2-10 cm in length. Despite these attractive features, SRS in LN has not been widely used for generating mid-IR radiation, presumably because of the presence of intrinsic and extrinsic absorption bands. In the present paper we demonstrate that high conversion efficiency can be obtained in LN even when the first Stokes line lies in the shoulder of an absorption band.

© 1981 Optical Society of America