Extended-cavity, tunable, GHz-repetition-rate femtosecond optical parametric oscillator pumped at 76 MHz.

We report the generation of tunable GHz-repetition-rate femtosecond pulses in a synchronously-pumped optical parametric oscillator (SPOPO) with extended cavity length pumped by a 76 MHz Kerr-lens mode-locked Ti:sapphire laser. In a SPOPO based on periodically-poled LiNbO3, insertion of a prism pair for dispersion compensation internal to the linear cavity provides stable output pulse trains of up to 14th harmonic of pump repetition-rate (1064 MHz) with 70 mW of average power for 1.45 W of pump. Near-transform-limited pulses down to 216 fs are achieved with wide tunability across 1500-1540 nm by continuous detuning of the SPOPO cavity delay over 8 microm.