Generation of tunable visible and near-IR light from 2.5 ps, high-power Ti:sapphire pulses by Raman shifting in hydrogen

Abstract

Stimulated Raman scattering was studied as a means to extend the tuning range of short-pulse Ti:sapphire lasers. Pulses of 2.5 ps duration at 784 and 392 nm with energies up to several millijoules were focused into a cell filled with up to 26 bar of hydrogen. With a pump wavelength of 392 nm, energy conversion efficiencies of 23 and 13% into first and second Stokes at 468 and 581 nm were found. Pulse durations of 1.3 and 1.4 ps were measured for the Stokes components, indicating a temporal shortening by a factor 2. The time-bandwidth product was determined to be similar to that of the pump pulse. The pump beam experiences significant self-phase modulation. Surprisingly the SRS threshold for 784 nm pump was found to be an order of magnitude higher. Energies of more than 0.2 mJ in the first Stokes at 1163 nm were measured.