Laser-diode pumped Cr:YAG passively Q-switched green laser by intracavity frequency-doubling with periodically poled LiNbO_3

摘要

A continue-wave (CW) laser-diode (LD) pumped passively Q-switched intracavity frequency-doubling green laser is reported in this paper. We used 3%at. Nd doped YVO_4 with size of 3 X 3 X 1mm as gain medium, Cr~(4+):YAG as a saturable absorber with small-signal transmission T_0=94% for passively Q-switch and periodically poled LiNbO_3 (PPLN) with the grating period Λ=6.1μm as a frequency doubler. The laser cavity was consisted of one face of the Nd:YV04, coated high-reflectance (HR) coating at 1.06μm and high transmittance (HT) at 0.808μm, and a 50mm radius of curvature output mirror with HR coating at 1.06μm and HT coating at 0.53μm. A CW 1W LD and a grading-refractive-index lens were used for the end-pumping. The output energy of the green laser is 0.96μJ with the pulse-width of 19ns. No green-noise problem exists in the green laser, because both the polarizations of fundamental wave and second harmonic wave are the same. Some theoretical results on the passively Q-switching and intracavity frequency-doubling are also reported.