Synchronously pumped, mid-infrared CdSe optical parametric oscillator

We present here the first continuous-wave, mode-locked synchronously pumped OPO based on noncritically phase-matched (NCPM) CdSe, with agile tuning of the idler over the range 9.1-9.7 μm, the longest wavelength achieved using a synchronously pumped OPO to date. Pump-wavelength-tuning over a wide range (necessary for the NCPM arrangement) was provided by the signal output of a periodically poled lithium niobate (PPLN) synchronously pumped OPO, operating close to degeneracy using a single PPLN grating period. The use of a diffraction grating to tune the signal of the PPLN synchronously pumped OPO was a key factor in obtaining clean, single-frequency pump conditions, with tuning achieved by simple grating rotation.