Electromagnetic Fields and Photonics Group

Nonlinear silicon photonics
Silicon photonics meets the electronics requirement of increased speed and bandwidth with on-chip optical networks. All-optical data management requires nonlinear silicon photonics. In silicon only third-order optical nonlinearities are present owing to its crystalline inversion symmetry. Introducing a second-order nonlinearity into silicon photonics by proper material engineering would be highly desirable. It would enable devices for wideband wavelength conversion operating at relatively low optical powers. 

Strained Si waveguides used to measure SHG: here we show atop-view optical image of the sample where a few waveguides are observed as yellow lines

We have recently shown, in the frame of a collaborative project with the University of Trento, the Bruno Kessler Foundation sponsored by cariplo Foundation, that a sizeable second-order nonlinearity at optical wavelengths is induced in a silicon waveguide by using a stressing silicon nitride overlayer. We carried out second-harmonic-generation experiments and first-principle calculations, which both yield large values of strain-induced bulk second-order nonlinear susceptibility, up to 40pm/V at 2.300 nm. We envisage that nonlinear strained silicon could provide a competing platform for a new class of integrated light ources spanning the near- to mid-infrared spectrum from 1.2 to 10 microns.

Summary of the SHG measurements. For details, see the reference.