The dawn of second order nonlinear photonics in silicon

Nature Materials (doi:10.1038/nmat3200) has just published online the first ever observation of second harmonic generation in strained silicon waveguide. It is well know that silicon is a centrosymmetric material which prevents second order nonlinearities. However by deforming the silicon structure with a stressing silicon nitride overlayer the italian collaboration lead by prof. Lorenzo Pavesi has been able to demonstrate the rise of a significant second order optical nonlinearities as big as the one of the widely diffused second order Lithium Niobate materials.

Until now nonlinear silicon photonics was founded on high-order nonlinear effects. The price for this was to need of high optical power. Now, second-order nonlinear activity considerably lowers such a “power threshold” and more interestingly allows silicon to enter in the realm of nonlinear crystals, where direct nonlinear down-conversion or other optical parametric processes can be achieved. All the ingredients to get mid-infrared or far-infrared parametric optical sources are now available and the race to demonstrate such exciting possibilities is open! This will open the MIR and FIR spectral regions to low cost, mass manufacturable and all integrated optical sources. In addition electro-optical effects which lead to low power and extremely fast optical modulator and switches can be engineered in silicon photonics. Another time, silicon has catch-up its limit whenever it is needed!

The collaboration involved researchers from University of Trento, Bruno Kessler Foundation, University of Modena & Reggio Emilia, University of Brescia, and from the CIVEN-consortium.

The article can be found at www.nature.com/nmat/journal/va … t/full/nmat3200.html

Provided by Universita degli Studi di Trento