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Switch takes computers to light-speed performance

Posted: 11 Oct 2013 ?? ?Print Version ?Bookmark and Share

Keywords:MEMS? NEMS? optical switch?

Long-distance communication is dependent on networks of fibre-optic cables that carry data encoded in nimble beams of light. Conventional computer circuits, however, still use relatively sluggish electronic circuits to process this data. Researchers from the A*STAR Institute of Microelectronics in Singapore have developed a device that could help computers reach light speed. According to them, the tiny mechanical system can switch a light signal on or off extremely quickly, potentially enabling all-optical computing and simplifying the interface between electronic and optical networks.

Various optical switching technologies already exist, including microelectromechanical systems (MEMS). These switches, however, take microseconds to flip from one state to another, far too slow for a computer application. The device is a much smaller nanoelectromechanical system (NEMS) that can switch in billionths of a second, with virtually no data loss.

"NEMS optical switches offer the potential for fast switching speed, low optical loss and low power consumption. And, they are easily integrated in large-scale arrays without complex packaging techniques," said Hong Cai, who headed the research team.

The researchers etched their device from a thin sheet of silicon, forming a flexible ring 60?m wide that is connected to a central pillar by four thin spokes. Two channels running through the underlying silicon skim past opposite edges of the ring; they act as waveguides for two beams of light. These channels pass no closer than 200nm from the ring.

When light carrying a signal passes through one of the channels, the light's electromagnetic field establishes resonant oscillations around the ring. This draws energy from the beam and prevents the data from travelling any furtherthe switch is effectively 'off'.

To flip the switch, a low-power beam of 10mW traveling along the other channel establishes a similar resonance that slightly warps the ring, bending its edges downwards by just a few nanometers. This warping motion changes the resonant frequency of the ring, preventing it from coupling to the signal beam and allowing the data to continue unimpeded. Switching the signal on took just 43.5ns, and the researchers observed a large difference in signal light output between the 'on' and 'off' states.

"As such, a low-power optical signal can be used to modulate a high-power optical signal at high speed," noted Cai. Her team is now working on integrating the devices into circuits.





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