Spectral broadening in chirped-pulse optical parametric oscillators based on KTiOAsO.

We report a chirped-pulse optical parametric oscillator (CPOPO) based on a (KTA) crystal. Due to the relatively low ratio between its second-order and third-order nonlinear susceptibility, a single KTA crystal could provide parametric gain and intra-cavity spectral broadening simultaneously in a CPOPO. Numerical simulations show that a signal-bandwidth of 390 nm can be obtained from a KTA-based CPOPO, and the pulses can be de-chirped with a width of ∼20 outside the OPO cavity. Experimentally, from a fiber-laser-pumped OPO with a 3-mm-long KTA crystal, we obtained a signal wave covering 1332-1667 nm, with a -20 bandwidth of 45.3 THz, around 12 times as much as the gain-bandwidth of the KTA crystal.