Four-wave mixing in porous silicon microring resonators

Third-order nonlinear optical phenomena have been intensively studied in integrated structures of crystalline silicon, Hydex, and silicon nitride for different applications, from classical to quantum photonics. As any other material, also porous silicon PSi is characterized by a third-order nonlinear response. Previous works have focused mainly on third-harmonic generation or two-photon absorption in multilayers. Recently, it has been shown that integrated high-quality ring resonators can be obtained starting from (PSi) multilayer. PSi slab waveguides are cheaper than silicon-on-insulator waveguides, and their porosity, thickness, and refractive index can be tailored by simply changing the fabrication parameters. Here we demonstrate low power four-wave mixing in an integrated structure made of porous silicon, namely a microring resonator with a quality factor of several thousand.