OPTICAL ELEMENT FOR SOLID LASER

PROBLEM TO BE SOLVED: To improve monochromaticity of laser beam of an SHG laser device while maintaining the high output of the laser beam. SOLUTION: On an excitation light incident-side end surface of a solid laser medium 3 as Nd:YAG crystal, a dielectric film 4 is formed which has a basic structure where an initial layer in contact with the solid laser medium 3 and an outmost final layer are SiO2film layers 4a of low refractive index and SiO2film layers 4a and Ta2O5film layers 4b of high refractive index are alternately stacked between the initial layer and final layer, such that one first half layer and second half layer each have a Ta2O5film layer 4b replaced with an Al2O3film layer 4c of intermediate transmittivity. Film thicknesses of the film layers 4a, 4b, and 4c and the displacement position of the Al2O3 film layer 4c are suitably adjusted to form a selective reflective and transmissive layer which transmits ≥99.9% of wavelengths 809 to 812 nm of excitation light, reflects ≥99.9% of the wavelength (946 nm) of basic wave light, and transmits an unnecessary wavelength (1,064 nm) excited by the solid laser medium 3 with high efficiency. COPYRIGHT: (C)2009,JPO&INPIT