Generation of 1.30- to 1.55-mu m tunable radiation from first Stokes Raman shifting in hydrogen

Raman shifting to the near-infrared, when possible, provides a simple and economical alternative to the optical parametric oscillator (OPO) or difference frequency mixing approach. We report the production of 1.30- to 1.55-mu m radiation from first Stokes Raman shifting in a single-pass, open (no capillary waveguide), hydrogen-filled Raman cell (constructed in-house) pumped with a Nd:YAG/dye laser combination operating near 900 nm. A maximum of 10 mJ (19% efficiency) of first Stokes energy was measured for the highest cell pressure (490 psia) and input pulse energy (53 mJ). The quality of the first Stokes output is similar to the dye laser output as indicated by polarization, shot-to-shot energy fluctuation, beam diameter, and linewidth. A characterization of the Stokes and anti-Stokes output was also conducted including one-dimensional spatial intensity profiles and output line dependence on input pulse energy and cell pressure. A large first Stokes conversion efficiency has been attributed to little production of higher-order Stokes and anti-Stokes lines.