Patent ID: 7760774

Claim:
A laser device operating at a fundamental frequency ω and adapted for frequency conversion of said fundamental frequency to a second harmonic frequency, said device comprising: a beamsplitter having partial reflectivity at the fundamental frequency ω to form a reflected fundamental beam, said beamsplitter having partial transmissivity at the fundamental frequency ω to form a transmitted fundamental beam, and said beamsplitter being highly transmissive of the second harmonic frequency; a complex optical cavity including said beamsplitter positioned within said complex optical cavity and dividing said complex optical cavity into: a first cavity part comprising an active (gain) medium for providing power enhancement of the fundamental frequency, said first cavity part formed between a laser cavity back mirror and the beamsplitter; and a second cavity part forming a self-regulating resonant reflector for the fundamental frequency ω for optimally out-coupling the fundamental frequency power circulating in the first cavity part and for further providing power enhancement of the fundamental frequency beam circulating in the second cavity part, said resonant reflector defining a first optical path for the transmitted fundamental beam between the beamsplitter and a first end mirror, said second cavity part further defining a second optical path for the reflected fundamental beam and for a second harmonic beam between the beamsplitter and a second end mirror, wherein said second optical path is different from the first optical path and wherein the first optical path and the second optical path do not overlap, said second cavity part comprising at least one nonlinear crystal placed in the second optical path for frequency conversion of the reflected fundamental beam to the second harmonic beam and for self-regulation, wherein the beamsplitter is positioned such that the first cavity part is on one side of the beamsplitter and the second cavity part is on the other side of the beamsplitter, whereby the first cavity part provides a lower power level at the fundamental frequency ω and the second cavity part, being a resonant reflector with respect to the first cavity part, provides a higher power level at the fundamental frequency ω to provide for an increase of the power of the second harmonic beam formed in the nonlinear crystal by the second harmonic generation process, the second harmonic beam being transmitted through the beamsplitter as the laser output.