All-optical switching in photonic crystals

Future devices for the information society may be based on optical treatment of information, requiring storage, transfer, and control of light with light. The basic electronic device, namely the transistor, is able to perform switching of an electrical signal. Thus, it is crucial to achieve switching of light by light, or all-optical switching, at low enough power and with low response time, enabling high modulation rate of the process. The use of nanocavities with high quality (Q) factor and low modal volume allows to reduce the required optical power and related heating effects.

We study all-optical switching of light propagating in silicon-based photonic crystal or photonic wire waveguides and interacting with high-Q nanocavities. Control of light propagating through the cavity is achieved by optical generation of free carriers, which modify the material refractive index and cause a shift of the cavity mode. This allows to switch the transmission of the probe beam from ON to OFF states, and vice-versa. The switching time is rapid (sub-nanosecond) as it is determined by electron-hole recombination, which is quite fast due to nonradiative effects at the hole sidewalls. Present research is focused towards improving the transmission characteristics, understanding the nonlinear mechanisms under various pumping conditions, and obtaining a precise determination of the time evolution of the switching.


L.C. Andreani, S. Azzini, M. Belotti, J.F. Galisteo-Lopez, M. Galli, D. Gerace, G. Guizzetti


Nanofabrication group, LTM-CNRS, Grenoble, France

Optoelectronics group, University of Glasgow, U.K.


Fondazione Cariplo 2007-2010 "Manipulation of light on nanometric scales for photonic and plasmonic applications"

MIUR-FIRB 2007-2011 "Analog and Mixed-mode Microelectronics for advanced systems"

Fondazione Cariplo 2005-2007 "All-optical switching in photonic crystals: towards the optical transistor"

Key publications:

All-optical switching in silicon-on-insulator photonic wire nano–cavities,

M. Belotti, M. Galli, D. Gerace, L.C. Andreani, G. Guizzetti, A.R. Md Zain, N.P. Johnson, M. Sorel, and R. M. De La Rue,

Optics Express 18, 1450-1461 (2010). PDF

All-optical switching in 2D silicon photonic crystals with low loss waveguides and optical cavities,

M. Belotti, J.F. Galisteo-López, S. De Angelis, M. Galli, I. Maksymov, L.C. Andreani, D. Peyrade, and Y. Chen,

Optics Express 16, 11624-11636 (2008). PDF