High-Power Diode-Pumped Single-Frequency Nd:YLF and Nd:YVO4 Lasers with Intra-cavity Second-Harmonic Generation to the Red Range

Single-frequency operation of diode-pumped Nd:YLiF₄ and Nd:YVO₄ 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 BiB₃O₆ (BiBO), LiB₃O₅ (LBO) or periodically-poled KTiOPO₄ (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.