Friday, February 29, 2008

Controlling Light by Photonic Crystals

The IEEE ACT chapter invited members to a talk on Controlling Light by Photonic Crystals, by Dr. Masaya Notomi, NTT, Japan at ANU. The topic sounded like science fiction, but turned out to be very down to earth. Dr. Notomi has been researching how to manipulate light in silicon microchips, much the way electrical signals are.

Photonic crystals have a regular lattice structure which effects the behavior of light in very specific ways. Examples in nature are the beautiful way light is reflected from butterfly wings and opals. However, much more regular structures are needed for practical applications. In place of the doping of silicon used for electronics, complex patterns of holes are etched in layers of the silicon. The arrangement of the holes gives different optical effects.

The simplest use for photonic crystals is to focus light, without the need for lenses. Light can be concentrated on a detector, or light from a LED source can be spread out. The light can be confined to a much smaller space than can be done with mirrors, or with refraction in a fiber optic cable. This could be used to transmit light from one point on a microchip to another.

Photonic Crystals can also be used to slow down light, by 50,000 times. This might be used in a light DRAM, which would have photons circulating slowly.

Injecting a second controlling light signal creates a light Flip Flop (bistable switch).

The wavelength of individual photons of light can also be changed, which might be used in quantum optical computers.


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