RESEARCH NEWS
Chips steer light in the right direction
“Record-setting” ‘optical phased arrays’ could lead to better laser rangefinders, smaller medical-imaging devices and even holographic TVs.
IF YOU WANT TO CREATE A MOVING LIGHT SOURCE, you have several possibilities. One is to mount a light emitter in some kind of mechanical housing - the approach used in, say, theatrical spotlights, which stagehands swivel and tilt to track performers. Another possibility is to create an array of light emitters and vary their “phase” - the alignment of the light waves they produce. The out-of-phase light waves interfere with one another, reinforcing each other in some directions but annihilating each other in others. The result is a light source that doesn’t move, but can project a beam in any direction.
Such “phased arrays” have been around for more than a century, used most commonly in radar transmitters, which can be as much as 100 feet tall.
Now researchers from MIT’s Research Laboratory of Electronics (RLE) have demonstrated a 4,096-emitter array that fits on a single silicon chip. Chips that can steer beams of light could enable a wide range of applications, including cheaper, more efficient, and smaller laser rangefinders; medical-imaging devices that can be threaded through tiny blood vessels; and even holographic televisions that emit different information when seen from different viewing angles. In a paper published this week in the journal Nature, the MIT team, led by Michael Watts, an associate professor of electrical engineering, report on two new chips. Both chips take in laser light and re-emit it via tiny antennas etched into the chip surface.
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www.siliconsemiconductor.net Issue I 2013
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