Femtosecond OPO pumped by a high power ytterbium rod-type fiber laser mode locked at harmonic repetition rates

Abstract

We report on an optical parametric oscillator (OPO) pumped by femtosecond pulses delivered by a large-mode-area, ytterbium-doped, rod-type fiber laser. This femtosecond laser that is mode locked at harmonic repetition rates of 108 MHz, 216 MHz, and 324 MHz provides an average output power of more than 4.5 W and tens of nJ per pulse. The repetition rate is changed by adjusting the pulse polarization inside the laser cavity. Remarkably, at all these repetition rates and without any modification to the cavity, the OPO delivers femtosecond signal pulses that are tunable from 1450 nm to 1700 nm, with an average output power higher than 1 W. Increasing the pump power of the rod-type fiber and decreasing the transmission of the OPO output coupler, we were able to run the OPO at 540 MHz.