PORTLAND, Ore., A cookbook developed by University of Toronto researchers describes how to fabricate efficient, large-scale, three-dimensional photonic band-gap (PBG) crystals. PBG materials enable light from micro-lasers to carry information on-chip the way fiber optics uses light for communication between chips.
"Now we are one step closer to an era of computers that use light instead of electrons," said Sajeev John, a professor in the University of Toronto's Department of Physics. "Basically we've discovered a whole new set of architectures for manufacturing nearly perfect photonic band gap materials that should provide an enormous increase in the available bandwidth for optical microchips."
The work was performed with physics graduate student Ovidiu Toader and Mona Berciu, a physics professor at the University of British Columbia.
Photonic band-gap materials are a class of dielectrics which are the optical analogs of semiconductors (they generate light by energizing their atoms accross the band gap). Many different approaches using diamond and other exotic materials have been explored. The search is on, because PBG materials foster coherent photon streams that can encode information the same way a stream of electrons does for semiconductors.
According to John's group, its PBG materials exhibit fundamentally new physics such as photon-atom bound states, lasing without a cavity mode and optical gap "solitons." The group cites possible applications for PBGs' to include zero-threshold micro-lasers with high-modulation speed, low threshold optical switches and all-optical transistors for future optical computers.
The photonic band-gap materials are superior to current semiconductors and can be manufacturing by applying nanoscale techniques to conventional silicon.
First a polymer template below a gold mask is bombarded with x-rays through an array of nanoscale holes in the mask, thereby removing tiny holes of polymer. Glass is them deposited to fill the holes and the remaining polymer is burned off. Silicon is then deposited throughout the regions around the glass template, and the glass removed
chemically, leaving the silicon riddled with the precise holes enabling its specific photonic band-gap characteristics.
The novelty of this material derives from the fact that when an atom has an electronic transition which lies within the photonic band gap, it does not spontaneously lase like a normal laser (spontaneous emission is the dominant loss mechanism in a conventional laser).
In John's PBG, the photon forms a bound state to the
atom, so that lasing can occur with zero pumping threshold, without mirrors and without a cavity mode since each atom creates its own localized photon mode. According to John, this should enable large arrays of nearly lossless on-chip microlasers for all-optical circuits.