ITHACA, N.Y. -- Cornell University researchers have demonstrated
for the first time a device that allows one low-powered beam of
light to switch another on and off on silicon, a key component
for future "photonic" microcircuits in which light replaces
electrons. Photonics on silicon has been suggested since the
1970s, and previous light-beam switching devices on silicon have
been demonstrated, but they were excessively large (by microchip
standards) or have required that the beam of light that does the
switching be very high-powered. The approach developed by Michal
Lipson, Cornell assistant professor of electrical and computer
engineering, confines the beam to be switched in a circular
resonator, greatly reducing the space required and allowing a
very small change in refractive index to shift the material from
transparent to opaque. The advancement of nanoscale fabrication
techniques in just the past few years has made it possible to
overcome some of the traditional limitations of silicon
photonics, Lipson s