Patent ID: 7593443

Claim:
A semiconductor laser excited solid-state laser apparatus having a nonlinear optical crystal installed in an optical resonator, where a solid-state laser medium is provided to be excited by the laser beam emitted from a semiconductor laser, for producing and outputting a harmonic of the fundamental wave oscillated in the optical resonator while detecting a portion of the harmonic and controlling the driving current of the semiconductor laser so that the harmonic remains constant, wherein the solid-state laser medium is Nd:YAG, the Nd:YAG has two ends thereof extending vertical to the optical axis, the Nd:YAG is arranged to be coated at one of the two ends which acts as one end of the optical resonator with an HR coating acting on the light produced by transition of energy from level 4 F 3/2 to level 4 I 11/2 , and the Nd:YAG functions as a band reflecting mirror with its two ends interfering the reflected light and its thickness along the direction of transmission of light is arranged of which the reflectivity becomes maximum to the light produced by transition of energy from sub level R 2 to sub level Y 3 and minimum to the light produced by transition of energy from sub level R 1 to sub level Y 1 .