Broadband light sources based on second-order nonlinear nanophotonics (Invited Paper)

Waveguides with second-order nonlinearities can realize an incredible variety of ultrafast behaviors by combining dispersive effects with multi-wave interactions. These systems have many degrees of freedom, including the phase-mismatch and group-velocity mismatch of the interacting waves. In this talk we discuss recently developed approaches for generating broadband coherent light in nonlinear nanowaveguides by engineering the dispersion relations of the interacting waves. We first discuss supercontinuum generation by group-velocity-matched second-harmonic generation. Here, spectral broadening occurs due to an interplay between phase-mismatch and pump depletion to form femtosecond amplitude modulations on the interacting fundamental and second harmonic. This approach has been used to realize octaves of bandwidth using less than 10 picojoules of in-coupled fundamental. In the second part of this talk, we discuss an approach to parametric down-conversion that relies on an interplay between parametric gain and temporal walk-off to realize arbitrarily long interaction lengths. This approach enables large (> 50 dB) parametric gains with picojoules of pump pulse energy.