Super-fast optical computers are a step closer thanks to research breakthroughs that may lead to silicon chips that can process information as electronic bits or flashes of light.

Two discoveries announced in the past week have sped the path to the fabrication of hybrid silicon chips with both electronic and photonic components.

The first discovery, published in this week’s issue of the journal Nature, foreshadows a future in which computers may run at terahertz speeds and, paradoxically, light will move much more slowly than it does today.

The other discovery, published in last week’s issue of the same journal, presents a new silicon-based microtransmitter that can send optical data at 100 Gbps — one-tenth of a terahertz.

Both teams are hoping their discoveries will fit within the present manufacturing framework — and can be built using the same techniques as silicon semiconductor chips (technically, “complementary metal-oxide semiconductor,” or CMOS).

Both must also work around what is both the inherent strength and weakness of optical computing and communications: The bits are always moving at the speed of light.

Here is where something called “slow light” comes into play. Having been studied in elaborate laboratory settings for years, light propagating in optically dense media — media that slow light’s propagation speed down considerably — has been an area of increasing interest in photonics. Slowing an optical bit down enables a computer to better buffer and route information traffic in much the same way that stoplights and speed limits are essential to controlling the flow of physical traffic.

The challenge has been that the only substantially light-slowing media were laser-illuminated gas clouds or specially prepared ruby crystals, neither of which are well suited for a CMOS chip.

However, a team of researchers led by Yurii A. Vlasov of IBM’s Thomas J. Watson Research Center announced this week that a grid of specially perforated silicon can slow the speed of light moving through its channels by a factor of 300.

By Mark Anderson

More here.