Abstract

For rapid wavelength tuning in optical parametric oscillators (OPOs), a mandatary requirement for many applications including spectroscopy and trace gas sensing, the use of crystals with fan-out grating design at a fixed temperature has been a potential approach, as it is a fast process compared to temperature tuning. In the continuous-wave (cw) regime, this technique has been successfully deployed using MgO:PPLN [1]. However, for direct pumping in the green to generate wavelengths <1 m, where short grating periods of ≲10 m are necessary, there have been significant challenges in quasi-phase-matched (QPM) fabrication technology. In particular, in the case of MgO:sPPLT, which has been demonstrated as a promising QPM material under green pumping [2], the challenges have been compounded by the growth and fabrication of the stoichiometric material itself. As such, in all earlier reports on cw green-pumped OPOs, wavelength tunability have been achieved by temperature tuning [2,3]. Moreover, due to the photorefractive damage issues under cw pumping, operation of such OPOs at room temperature, avoiding instabilities due to temperature fluctuations, has remained difficult. Here we report what is to our knowledge the first realization of green-pumped cw OPO operating at room temperature using fan-out grating MgO:sPPLT, providing wide tunability from the red to the mid-infrared. The OPO, pumped in the green, can provide continuous tuning across 638–1021 nm in the signal, with corresponding idler tunable across 1110–3191 nm. The pump laser used is a solid-state laser delivering up to 10 W of power at 532 nm, and the crystals used are a pair of 29-mm-long, 31-mm-wide and 0.8-mm-thick MgO:sPPLT with fan-out gratings (_=7.8-9.5 m, _=9.4-11.5 m). The OPO is configured in ring cavity with two concave mirrors (r=−100 mm), a plane mirror, and a plane output coupler for the signal. The single-pass idler is separated from the pump using a dichroic mirror.

© 2017 IEEE