Adjusting third-order nonlinear properties in silicon triply resonant nanobeam cavities

Abstract

We propose the use of triply resonant silicon photonic structures, based on a set of three coupled silicon nanobeam cavities, to engineer third-order nonlinearities. We show that a judicious selection of the opto-geometrical parameters allows a nearly independent tuning of the linear and nonlinear properties of the system. We demonstrate that longitudinally shifting the central cavity weakly affects the system nonlinear properties while strongly changing its resonance wavelengths. In contrast, longitudinally shifting one of the side cavities leads to a significant variation of the self-phase modulation, cross-phase modulation, and four-wave mixing nonlinear overlaps, while the linear properties of the three-cavity photonic molecule are then only moderately tuned. This geometrical control of the nonlinear properties of photonic molecules opens new degrees of freedom for the realization of small footprint and efficient optical switching and frequency conversion devices.