Carrier-envelope offset frequency stabilization in a femtosecond optical parametric oscillator without nonlinear interferometry.

By exploiting the correlation between changes in the wavelength and the carrier-envelope offset frequency (fCEO) of the signal pulses in a synchronously pumped optical parametric oscillator, we show that fCEO can be stabilized indefinitely to a few megahertz in a 333 MHz repetition-rate system. Based on a position-sensitive photodiode, the technique is easily implemented, requires no nonlinear interferometry, has a wide capture range, and is compatible with feed-forward techniques that can enable fCEO stabilization at loop bandwidths far exceeding those currently available to OPO combs.