SINGLY RESONANT CONTINUOUS-WAVE MODE-LOCKED KTIOPO4 OPTICAL PARAMETRIC OSCILLATOR PUMPED BY A ND-YAG LASER

We present detailed design considerations and performance of a singly resonant cw mode-locked optical parametric oscillator based on KTiOPO4. The oscillator is synchronously pumped by 2.2-ps, 1.064-mum pulses at a 75-MHz repetition rate with 4-W average power generated by temporal compression of pulses from a lamp-pumped mode-locked Nd:YAG laser. We obtained output pulses 2-3 ps long with hundreds of milliwatts of average power from 1.57 to 1.59 mum in the signal branch and from 3.21 to 3.30 mum in the idler branch. At three times above threshold we measured the pulse width of the 1.573-mum signal to be approximately 2.8 ps, and the corresponding spectral width was approximately 1.5 nm, indicating that the time-bandwidth product is 0.51. The total conversion efficiency as measured by the pump-pulse depletion is 15%. With active stabilization of the pump laser, the amplitude fluctuation of the oscillator is <15% peak to peak.