Patent ID: 7466728

Claim:
Optical apparatus comprising: an optical resonator having a resonator axis and arranged to cause a beam of optical radiation having a first-wavelength to circulate therein in one direction only along said resonator axis; and an optically nonlinear crystal located in said optical resonator on said resonator axis, said optically nonlinear crystal being arranged to convert said circulating first-wavelength wavelength radiation to optical radiation having a second wavelength shorter than said first-wavelength, and to reflectively couple said second-wavelength radiation out of said resonator at an angle to said resonator axis and wherein said optically nonlinear crystal has an input-face, and first and second output-faces and is arranged such that said circulating first wavelength radiation enters said crystal via said input face thereof and exits said optically nonlinear crystal via said first output face thereof, and such that said second-wavelength radiation is coupled out of said resonator via said second output face of said optically nonlinear crystal.