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This talk will provide an overview of the latest advances in OPO technology based on novel nonlinear materials such as CdSiP2 (CSP), orientation-patterned GaP (OP-GaP), and MgO:sPPLT, in combination with solid-state and fiber pump laser technology. In the ultrafast time-scales, we have achieved operation of femtosecond OPOs into deep-IR at wavelengths as long as ~8 um by exploiting internal cascaded parametric generation based on MgO:PPLN and CSP using the Kerr-lens-mode-locked (KLM) Ti:sapphire laser as primary pump source, or by external cascaded pumping using a commercial near-IR femtosecond OPO as the intermediate pumping step. More recently, we have also demonstrated successful operation of deep-IR femtosecond OPOs based on CSP at wavelength beyond 8 um by direct pumping with the KLM Ti:sapphire laser, and without the need for intermediate cascading step. We have also recently shown that the development of high-repetition-rate ultrafast OPOs in the picosecond time-scale into the deep-IR is possible by direct pumping using Yb-fiber lasers at 1.064 um. The major improvements in the optical quality of the CSP crystal with low transmission loss over long interaction lengths have made it possible to overcome the low nonlinear gains under low pumping intensities, thus enabling us to develop the first high-repetition-rate picosecond OPO based on CSP and with wavelength tunability out to 6.7 um. In the cw regime, we have demonstrated new a concept for frequency comb generation based on OPOs in doubly-resonant oscillator configuration with dispersive cavities. Using this new concept in a cw OPO based on MgO:sPPLT and pumped at 532 nm in the green, we have generated broadband cw spectra centred at 1064 nm with ~9 THz bandwidth containing >42000 modes. These developments have opened the way for the advancement of OPO sources in new directions and their potential use in a wide range of novel applications including optical microscopy, spectroscopy, and imaging.
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