Abstract: A device for coherent optical and infrared second harmonic generation comprising an active laser element, a cavity Q-switched to the fundamental frequency of the active laser element, thereby ensuring formation of a zone of intersection of the fundamental frequency beams, and a nonlinear crystal placed inside the fundamental frequency cavity in the fundamental frequency beams intersection zone, said crystal generating the second harmonic under noncollinear synchronism conditions and transparent for both the fundamental frequency and second harmonic. The proposed device permits second harmonic generation under non-collinear synchronism conditions in a nonlinear crystal. This allows a spectroscopically pure second harmonic to be obtained and widens the field of nonlinear crystals application.