Stimulated Raman Scattering in Vapor-Deposited Solid Hydrogen Film

Abstract

The solid para-hydrogen film was prepared by depositing the para-hydrogen vapor onto a sapphire substrate. From the stimulated Raman scattering experiment using two ns-lasers whose laser-frequency difference is equal to the fundamental vibrational transition of the solid para-hydrogen, we observed the collinear generation of Raman sidebands. The high-order Raman sidebands were obtained under the strong pumping intensity (≥230 MW/cm2). The generated five anti-Stokes(AS)-Raman sidebands extend from ultraviolet (292 nm for AS 5 band) to visible (565 nm for AS 1 band) region. Also, we found that the first AS-Raman signal shows weak rotational components as well as a strong vibrational line. From the experiment that makes the multimode probe beam beat with the prepared Raman coherence, we found that the prepared Raman coherence replicates the probe beam to its Raman sidebands. The frequency conversion efficiency from the probe beam to the first AS-Raman sideband rises to the maximum (4.7%) at 284 MW/cm2, and then falls with the increase of the pumping intensity. This is thought to be due to the fact that some molecules in the first vibrational level incline to go to the higher vibrational level under the higher pumping intensity. For the strong pumping intensity (290 MW/cm2), four anti-Stokes and one Stokes Raman sidebands of the probe beam were generated.