High efficiency mid-IR generation by Raman down conversion in liquid nitrogen

Abstract
Radiation at 3.92 μm was generated by focusing a 2.05-μm Ho:YLF laser in a single-pass liquid nitrogen Raman cell. The 3.92-μm pulses (∼10 mJ, ∼10 ns) were Gaussian, ≥90% linearly polarized, and approximately diffraction limited. Photon conversion efficiency exceeding 95% was achieved.