Pulse compression effects of passive mode locker in ultrafast optical parametric oscillator

The pulse compression effects of passive mode locker, such as graphene and Kerr lens medium, which has been inserted into a synchronously-pumped optical parametric oscillator (SPOPO) pumped by pulse laser, and a continuous-wave (cw) pumped actively mode-locked OPO has been studied theoretically. By solving the nonlinear coupled-wave equations in the plane-wave approximation, we simulate the relations of the pulse width and peak power of the signal pulses to the normalized aperture radius, the nonlinear crystal length and the beam radius on the nonlinear crystal. The numerical results indicate that the Kerr lens medium and graphene are both favorable for the pulse compression in the SPOPO, and each of them has different advantages. Whereas in the actively mode locked OPO, the Kerr lens medium may be a better alternative for the pulse compression.