Generation of mid-infrared emission with a 3.1-4.5 μm instantaneous bandwidth from a chirped-pulse optical parametric oscillator.

We report a broadband optical parametric oscillator (OPO) pumped by a Yb-doped fiber laser system. By utilizing a 300 μm long magnesium-doped periodically poled LiNbO crystal as the parametric gain medium and configuring the OPO as a chirped-pulse oscillator, we obtained mid-infrared emission having an instantaneous bandwidth covering 3084-4466 nm. This result represents, to the best of our knowledge, the widest instantaneous bandwidth obtained from a Yb-fiber-laser-pumped singly resonant OPO, demonstrating the immense potential of chirped-pulse oscillation in scaling the instantaneous bandwidth of ultra-fast OPOs. Moreover, we performed a numerical simulation of chirped-pulse OPOs (CPOPOs) and revealed that the spectral profile of the output from a CPOPO was relevant to both the parametric gain profile of the nonlinear crystal and the intra-cavity high-order dispersion.