Methods for extending mode-hop-free tuning using a dual-cavity, pump-enhanced optical parametric oscillator

Summary form only given. Continuous-wave (CW) optical parametric oscillators (OPOs) are well suited to high-resolution spectroscopy applications. Due to their low thresholds there has been interest in using CW OPOs in which two of the interacting fields are resonated in the same cavity (e.g. doubly-resonant OPOs (DROs) and pump-enhanced singly-resonant OPOs (PE-SROs)). Common-cavity DROs have exhibited signal and idler tuning ranges equivalent to several cavity free-spectral-ranges (FSRs), but PE-SROs are limited by mode-hopping to typically less than one FSR unless the phase-matching is tuned synchronously with pump frequency. The idler tuning range is limited in both cases to only a fraction (/spl nu///sub t//spl nu//sub p/ where /spl nu//sub 1/ and /spl nu//sub p/ are the idler and pump frequencies respectively) of the pump-laser tuning range. We report extended spectral tuning in PPLN based PE-SROs. Coarse wavelength tuning from 2.7 to 5 /spl mu/m is possible and smooth single-frequency scanning ranges of over 10 GHz are demonstrated. The latter is accomplished by a novel dual-cavity configuration in which mode-hopping is suppressed. We also report a further variant of the dual-cavity method in which the signal cavity is scanned synchronously with the pump cavity to ´track´ the phase match bandwidth resulting in much larger tuning ranges than in the mode-hop suppression method.