SUM FREQUENCY LIGHT GENERATION METHOD AND SUM FREQUENCY LIGHT GENERATION APPARATUS ADAPTABLE FOR WIDE-BAND WAVELENGTH CONVERSION

摘要

A nonlinear optical crystal allowing type 2 phase matching multiplexes a fixed wavelength light having an angular frequency .omega.D and a variable wavelength light having an angular frequency .omega.S, with the polarization directions thereof being perpendicular to each other, so as to produce a sum frequency light having an angular frequency .omega.D + .omega.S. When multiplexing the fixed wavelength light and the variable wavelength light through the nonlinear optical crystal, a controlling section controls the polarization direction of the fixed wavelength light so as to be parallel to a predetermined reference axis within a plane vertical to a phase matching direction of the nonlinear optical crystal. Even when the wavelength of inputted light is changed, the predetermined reference axis is a single axis which maintains parallelism with the crystal axis of the nonlinear optical crystal.