METHOD FOR CONVERTING LASER BEAM WAVELENGTH AND DEVICE USING THIS METHOD

摘要

PROBLEM TO BE SOLVED: To make use nonlinear crystals usable over a long period of time without the impairment thereof by a laser beam and to stably obtain high wavelength conversion efficiency by continuously passing the laser beam having the laser intensity below the threshold of the nonlinear crystals through the nonlinear crystals disposed in plural pieces. SOLUTION: The laser beam having the laser intensity below the threshold of the nonlinear crystals is continuously passed through the nonlinear crystals 1 to 5 disposed in plural pieces. The flat plates of the nonlinear crystals 1 to 5 are arranged perpendicularly on a nonlinear crystal holder attached with an angle adjuster 6 for phase matching of the laser beam in a laser beam wavelength conversion section. Both of a type I and type II are adequately usable for the nonlinear crystals. The type I refers to the nonlinear crystal having the incident angle of the laser beam of the case where the incident angle is determined from a Sellmeier's empirical formula by using the refractive index expressed by equation I. The type II refers to the nonlinear crystal having the incident angle determined similarly from the Sellmeier's empirical formula by using the refractive index expressed by equation II. In the equations,λdenotes a wavelength andθm ,ϕm denote incident angles.