One of the big hold-ups on the development of optical (as opposed to electronic) circuits has been that there were no clear alternatives to silicon, which never seemed up to the job; certainly there was nothing with comparable fabrication infrastructure in place. However, this may have changed. Ansheng Liu of Intel in Santa Clara, California, and colleagues have shown that a MOS-type capacitor structure placed in a silicon optical waveguide can have its index of refraction varied by an applied voltage. The resulting device can provide phase- shift modulation with a bandwidth of more than 1 GHz, exceeding earlier speed records by a factor of about 50. Such progress, and the obvious ease with which electronics in silicon could be mixed with nascent silicon-optics technology, could lead to amazing devices in future.
Further reading
A Liu et al. 2004 Nature 427 615.