Beam shaping to suppress phase mismatch in high power second-harmonic generation

A deliberate pattern of distributing the radiation energy of a high power laser can minimize the steady-state thermal gradients in a nonlinear crystal, thus permitting a large increase of the average powers of such systems. The theory of the two main techniques of beam shaping-fanning and scanning-is developed. Results of several experiments based on this theory are given. Experimental techniques, including some not yet attempted, are discussed.