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Laser controls photonic silicon chip

Posted: 13 Sep 2010 ?? ?Print Version ?Bookmark and Share

Keywords:photonics? silicon chips? optical signals?

A technique that harnesses vapor-filled optical waveguides on silicon chips to process data streams encoded on light, enabling optical signals to be slowed down and switched on-chip, has been reported by researchers from the University of California at Santa Cruz (UCSC).

The technique removes the need to convert optical signals to electrical signals in applications that detect, buffer, multiplex and store photonic information.

spectroscopy at UCSC

UCSC fabricates arrays of waveguides on a single four inch silicon wafer, here showing 32 atomic spectroscopy chips using them.

"We can potentially use this to create all-optical switches, single-photon detectors, quantum memory devices, and other exciting possibilities," explained Holger Schmidt, an electrical engineer and professor at UCSC.

The technique demonstrates electromagnetic optical switching on a fully self-contained silicon chip. It uses quantum interference effects in an on-chip hollow-core optical waveguide filled with rubidium vapor. A control laser switches the optical signal on and off, and slows the data stream's speed by up to 1,200 times.

"By changing the power of a control laser, we can change the speed of lightjust by turning the power control knob," noted Schmidt.

The control laser makes the rubidium vapor transparent to the optical signal, thereby switching it on and off, by virtue of putting the rubidium atoms in a coherent superposition of two quantum states. This so-called "electromagnetically induce transparency" allows optical signals to be both switched and slowed by a quantum effect, potentially facilitating the creation of quantum communication networks using silicon photonic chips.

The researchers have already been able to use the rubidium filled waveguides to develop an atomic spectroscopy device on a single chip, which the group is fabricating 32 at a time on a single silicon wafer.

Researchers at Brigham Young University also contributed to the work, including John Hulbert, Evan Lunt, Katie Hurd, and Aaron Hawkins. Bin Wu, a doctoral candidate at UCSC, performed much of the work. Funding was provided by the Defense Advanced Research Projects Agency and the National Science Foundation.

- R. Colin Johnson
EE Times

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