Continuous-wave optical parametric oscillators pumped by external-cavity single-mode diode lasers

Abstract

Summary form only given. Single-mode diode lasers are attractive pump sources for CW-OPOs due to their compact size, tunability and efficiency. In spite of their relatively low output powers, the availability of quasi-phase-matched materials such as PPLN has enabled the demonstration of practical OPOs pumped by such diode lasers and having thresholds as low as 16 mW. However, simple Fabry-Perot diode lasers typically exhibit poor frequency stability which limits the usefulness of diode-pumped OPOs as stable sources for applications such as spectroscopy. The use of external grating feedback to stabilise diode lasers is a well established technique. Although external cavity operation generally reduces the power available from diode lasers, the thresholds typically obtained with PPLN doubly-resonant OPOs (DROs) and pump-enhanced single-resonant OPOs (PE-SROs) are still within the range of these pump sources. We have developed an external-cavity diode laser in a Littrow configuration, producing up to 60 mW at /spl sime/810 nm, and used this source to pump a PPLN DRO. Stabilised single-mode operation of the DRO for over five minutes was achieved using a servo-control system and was limited by the mechanical stability of the DRO. Previously, with a free-running diode laser, stabilisation was limited by mode-hopping of the pump to less than one minute.