Abstract

Raman shifting of Ho:YLF laser radiation provides an efficient method of generating coherent light in mid-IR atmospheric windows. Previous experiments at NRL have shown that stimulated Raman scattering (SRS) of 2.05-μm Ho:YLF radiation in liquid nitrogen (LN) produces 3.92-μm radiation with high conversion efficiency.¹ However, instabilities in the Ho:YLF laser then employed precluded systematic performance evaluation of the SRS down- conversion. We have now incorporated major improvements into the Ho:YLF laser design which minimize variations in spatial mode and pulse shape. This has enabled us to investigate in detail the 2.05 → 3.92-μm downconversion using SRS in LN. We demonstrate that photon conversion efficiencies exceeding 95% can be achieved in a small single-pass cell utilizing unpurified LN. We also report preliminary experiments on 2.05 → 3.01-μm SRS In liquid oxygen (LO) where high downconversion efficiencies have also been obtained.

© 1983 Optical Society of America