Distributed feedback in lasers due to parametric interaction: transient effects and nonlinear conditions

A theoretical analysis is made of a laser system with distributed feedback due to a parametric interaction of waves in a nonlinear medium. The threshold conditions for this system are found allowing for partial spatial coherence and pump nonmonochromaticity. A calculation is made of the time characteristics of a coherent pulse emitted in the direction opposite to that of a pump wave just above the threshold. An evaluation is also made of the power efficiency of conversion of a parametric pump wave into signal and idler waves under steady-state stimulated emission conditions.