Patent ID: 7113325

Claim:
A nonlinear optical conversion device designed for operation at high optical power levels comprising: a nonlinear crystal having entrance and exit surfaces allowing input and output laser beams to propagate in the phase-matching plane for a desired nonlinear generation process, said nonlinear generation process involving a nonlinear interaction in said nonlinear crystal and resultant conversion of power in one or two input beams into power in the output beam, said nonlinear crystal characterized by absorption and resultant modification of the crystal properties by the power in the output beam, said modification with the potential for reducing the efficiency of the nonlinear process in said crystal, and said nonlinear process involving critical phase-matching in the nonlinear crystal in which the powers in the output beam and input beam or beams propagate in different directions through the process of Poynting vector walk-off, said input beam or beams being of a sufficiently small beam dimension in the phase-matching plane such that said output beam spatially separates from said input beam or beams in a length small compared to the length of said crystal, thereby removing much of the modification of the properties of said nonlinear crystal from the region of the nonlinear interaction involving said input beams, and leading to improved conversion of power in the input beams over configurations in which the spatial separation of the input and output beams is minimal over the length of said crystal.