Analysis of stimulated Raman scattering in waveguides

Stokes radiation, excited by a giant pulse radiation propagating along a rectangular wavegulde, is analyzed in this paper. Equations are established and solved for an arbitrary shape of the giant pulse. At high gains the stimulated radiation is emitted at all angles. The maximum output is almost perpendicular to the exciting beam, and it decreases as the forward and backward directions are approached. Forward-backward ratios are sensitive to the detailed shape and magnitude of the laser pulse. The large forward-backward ratio for intense short laser pulses accounts for the observed results, which are illustrated for a square and a parabolic pulse. In practice, a large number of waveguide modes are simultaneously excited, resulting in intense excitation of vibrational modes in the medium, and enhancement of the inverse Raman effect and of anti-Stokes generation.