Abstract

Optical parametric generation is a convenient means of providing widely tunable laser radiation over wavelength regions not directly accessible by many of the more conventional tunable sources. Despite their many potential advantages, interest in parametric devices has in the past remained largely limited owing to a lack of suitable non-linear materials of high optical quality and laser pump sources of sufficiently high coherence and intensity. However, the recent emergence of novel nonlinear crystals with excellent optical and mechanical characteristics such as BBO, KTP, and the newly discovered material LBO, has renewed interest in optical parametric oscillators (OPO’s) for the generation of tunable radiation. Advances in laser technology have also led to the development of highly coherent, high-power laser sources in new regions of the spectrum which may now be effectively used as pumps for OPO’s. In particular, the advent of diode-pumped solid-state lasers has provided a unique opportunity for the development of a new generation of compact, efficient, all-solid-state sources of broadly tunable radiation based on OPO’s. To this end, we describe a new source of picosecond pulses based on an OPO that is synchronously-pumped by an all-solid-state laser and broadly tunable over the entire range 652 nm-2.65 μm, using a single non-linear crystal. We have previously reported the operation of similar devices based on KTP and LBO in doubly-resonant oscillator (DRO) configurations.^[1,2] Although this mode of operation is generally characterised by low oscillation thresholds, the spectral and/or amplitude stability of the output can often be poor due to mode- or cluster-hopping effects, thus requiring stringent control of the pump laser and OPO cavity lengths. We have thus sought to explore the feasibility of extending the approach to singly-resonant oscillators (SRO’s), and here demonstrate that even with the pump power levels available from the most modest diode-pumped solid-state lasers, and appropriate mirror sets, singly-resonant operation of such oscillators may be readily achieved.

© 1992 IQEC