Picosecond synchronously pumped optical parametric oscillator delivering transform-limited pulses in the degeneracy region

We report about a PPKTP optical parametric oscillator synchronously pumped by a picosecond Ti:Sapphire laser. The system is tunable in the spectral region around 1.55 lm which corresponds to the degeneracy wavelength. Nevertheless, it is able to deliver transform-limited pulses thanks to the insertion of a properly designed birefringent filter which ensures single-frequency operation as well. The resonating wavelength can be tuned for more than 100 nm by a simple rotation of the filter and is proven to be insensitive to cavity length detuning and pump wavelength drift.