Two-crystal, synchronously pumped, femtosecond optical parametric oscillator.

We demonstrate a femtosecond optical parametric oscillator based on two nonlinear crystals synchronously pumped by a single ultrafast laser for efficient intracavity signal amplification and output power enhancement. By deploying two identical MgO:PPLN crystals in a single standing-wave cavity, and two pump pulse trains of similar average power from the same Kerr-lens-mode-locked Ti:sapphire laser, a minimum enhancement of 56% in the extracted signal power is achieved, with un-optimized output coupling, when temporal synchronization between the two intracavity signal pulse trains is established, resulting in a corresponding enhancement of 49% in pump depletion. Using intracavity dispersion control, near-transform-limited signal pulses with clean spectrum are obtained.