Influence of spatial and temporal noncoherence of the pump radiation on the Stokes signal amplification

An experimental investigation was made of the interaction of a narrow-band Stokes signal with a nonmonochromatic pump wave for different angles θ_sp between the two interacting waves. The efficiency of conversion fell strongly on increase of the angle θ_sp because of the spatial noncoherence of the pump wave. It was found experimentally that at sufficiently high values of the angle θ_sp the critical intensity ceased to depend on the width of the pump line.