Second harmonic generation

Claim 1

A second harmonic generator for generating a second harmonic laser light comprising: an excitation laser; a laser medium for generating a fundamental wave laser light by the light of the excitation laser, said fundamental wave laser light having an ordinary ray element and an extraordinary ray element; a non-linear optical crystal element provided within an optical resonator formed by first and second mirrors for generating a second harmonic laser light by the fundamental wave laser light reciprocated in the optical resonator, said optical resonator holding the fundamental wave laser light in unpolarized status; a birefringent element further provided within the optical resonator, with the optical axis in the extraordinary ray direction being inclined at a specific azimuth angle against the optical axis of the non-linear optical crystal element in the extraordinary ray direction; whereby, the output of the second harmonic laser light emitted from the resonator is stabilized.