Determination of the Raman gain coefficient in leucosapphire

An experimental investigation was made of stimulated Raman scattering in leucosapphire ({alpha}-Al{sub 2}O{sub 3}) pumped at the wavelength {lambda} = 532 nm by pulses of {tau} =30 ps duration (the second harmonic of an Nd{sup 3+} : Y{sub 3}Al{sub 5}O{sub 12} laser). The Raman gain coefficient was determined for the first vibrational Stokes component with the wavelength {lambda} = 544 nm, corresponding to a Stokes shift of 419 cm{sup -1}. This gain coefficient varied from 2.5 x 10{sup -10} to 4.6 x 10{sup -10} cm W{sup -1}, depending on the relative orientation of the leucosapphire crystal axes relative to the plane of polarisation and to the axis of the pump beam. The energy conversion efficiency was {eta} =1% when the pump intensity was 100 GW cm{sup -2}. (nonlinear optical phenomena and devices)