title: Approximate theory of Stokes amplification and conversion valid at large gain.
abstract: We predict Stokes-beam divergence, origin, and gain for large-gain Raman amplifiers as functions of pump-beam divergence and pump power in terms of simple analytical expressions. Stokes divergence is found to peak at a pump power twice above threshold. Results are in excellent agreement with exact computer solutions and explain recent experimental observations.
authors.forename: K J
authors.initials: KJ
authors.lastname: Drühl
authors.forename: S
authors.initials: S
authors.lastname: Shakir
authors.forename: M
authors.initials: M
authors.lastname: Yousaf