IBM Harnesses "Slow Light" for Optical Communications

Researchers at IBM were able to slow light down to less than 1/300th of its usual speed by directing it down a carefully designed channel of perforated silicon called a "photonic crystal waveguide." The photonic crystal waveguide is a thin slab of silicon punctuated by regular arrays of holes that scatter light. The pattern and size of the holes gives the material a very high refractive index -- the higher the refractive index, the slower the light. Heating the waveguide locally with a small electrical current alters the refractive index, allowing the speed of light to be quickly tuned over a large range with very low applied electric power.


IBM said the innovation opens the door to the possibility of complex light-based circuits with footprints not much larger than semiconductor circuits. The device was manufactured using a common CMOS processes.


The report on this work, "Active control of slow light on a chip with photonic crystal waveguides" by Yurii A. Vlasov, Martin O'Boyle, Hendrik F. Hamann, and Sharee J. McNab of IBM's T.J.Watson Research Center in Yorktown Heights, N.Y. is published in the November 3 issue of Nature. This work was partially supported by the Defense advanced Research Agency (DARPA) through the Defense Sciences Office program "Slowing, Storing and Processing Light".http://domino.research.ibm.com/comm/pr.nsf/pages/news.20051103_photonics.html