Consecutive quasi-phase-matched generation of the third harmonic of the radiation from an Nd : YAG laser in a periodically poled Y : LiNbO3 crystal

Consecutive generation of the third harmonic (i.e. generation of radiation with the doubled frequency followed by frequency summation) radiation from a Q-switched Nd:YAG laser (lambda = 1.064 mu m) was observed in a Y:LiNbO3 crystal polarised periodically along the z axis. The modulation period of t he nonlinear susceptibility was similar to 60 mu m. The second and third ha rmonics of the radiation were generated respectively in the ninth and thirt y-third quasi-phase-matching orders.