Intracavity second-harmonic generation of diode-pumped continuous-wave, single-frequency 1.3 µm Nd:YLiF₄lasers

Abstract

We report on the comparative performance of intracavity frequency-doubled continuous-wave (cw) single-frequency Nd:YLiF4 ring oscillators lasing on the ~1.3 µm 4F3/2–4I13/2 transition using either periodically poled KTiOPO4 (ppKTP) or birefringent-phase-matched BiB3O6 (BiBO) and LiB3O5 (LBO) nonlinear crystals. Using a single-end diode pumping scheme, a watt-level of tunable single-frequency radiation in the 650–660 nm red spectral range was obtained, limited by the saturated gain and thermal effects of the laser crystal. The best performance in terms of red beam quality, tuning range and power (~1 W) was achieved with the temperature-tuned highly nonlinear (second-order nonlinear effective coefficient deff~8.9 pm V−1) ppKTP crystal at 657 nm. Up to ~0.7 W of single-frequency power with a degraded transverse beam quality could be achieved at 661 nm using a type-I cut critically phase-matched BiBO crystal (deff~2.5 pm V−1), while the insertion of a type-I cut LBO crystal (deff~0.8 pm V−1) yielded less than 0.3 W red power at identical operating conditions. Owing to a robust passive frequency stability and to their intrinsic short-term narrow linewidth (Δν<3 MHz), these solid-state laser sources are well suited to high-resolution spectroscopy in the lower wavelength part of the red spectrum.