Twohyphen;photon resonant fourhyphen;wave parametric amplification

摘要

Fourhyphen;wave parametric amplification is discussed when the incident pump frequency is close to a twohyphen;photon resonant transition in the material. Expressions for the amplification factor are obtained both under steadyhyphen;state and pulsed excitation and also for a nonmonochromatic pump. For ultrashorthyphen;pulse excitation an rsquo;rsquo;energy theoremrsquo;rsquo; is derived and discussed. In steady state, expressions for optimum frequency and intensity are obtained. The amplification factor under broadhyphen;band excitation decreases with increasing pump linewidth.