Applied Physics

Two Speeds at Once

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Science  04 Jan 2008:
Vol. 319, Issue 5859, pp. 13
DOI: 10.1126/science.319.5859.13b

In the seemingly never-ending quest to speed up data transfer, light constitutes the ultimate communications carrier. However, the speed of light through a medium is generally constant, making photon storage and on-chip optical signal processing difficult tasks to implement. To slow things down, coupling microring resonators to an optical waveguide can effectively delay the propagation of photons. It has also been shown that the dispersion properties of these devices can distort the pulse profile so that the speed of light appears to be exceeded, providing so-called fast-light. From a practical viewpoint, it would be desirable to combine both of these properties in a single optical device. Recent work has found that these microring resonators are birefringent with respect to the polarization of the propagating light; i.e., one polarization simultaneously propagates faster than its orthogonal counterpart. From calculations, Fietz and Shvets show that by using light of mixed polarization and adjusting the mixing angle of that light and the number of microring resonators along the waveguide, a tunable delay time between polarized wave packets of incoming light should be readily achieved. — ISO

Opt. Lett. 32, 3480 (2007).

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