High-Power Diode-Pumped Single-Frequency Nd:YLF and Nd:YVO 4 Lasers with Intra-cavity Second-Harmonic Generation to the Red Range

Single-frequency operation of diode-pumped Nd:YLiF 4 and Nd:YVO 4 continuous-wave (cw) ring lasers are investigated in the 1.31-1.34 mum range, together with their intracavity second-harmonic generation to the red spectral range (0.65-0.67 mum) using either BiB 3 O 6 (BiBO), LiB 3 O 5 (LBO) or periodically-poled KTiOPO 4 (ppKTP). Smooth single-longitudinal mode wavelength tuning over Deltalambda~3-4 nm within the gain bandwidths could be achieved, with a watt-level output at gain centers in the near-IR and red range. Unlike with the birefringence phase-matched crystals, second-harmonic generation using ppKTP leads to various dynamical regimes, from narrow-band continuous-wave to broadband self mode-locked operation triggered by chi (2) :chi (2) second-order Kerr-lens cascaded nonlinear interactions.