Crystal bends light hard, saves space.

For air travelers who can't fly direct, landing and transferring to another jet can eat up a lot of the speed advantage of planes. Similarly, telecommunications currently bog down at switching hubs, where optical signals must shunt briefly to less efficient, electronic routing equipment.

To eliminate the bottleneck, researchers are striving to develop miniaturized, all-optical switching circuits. "To do this, light is going to have to go around sharp corners," says John D. Joannopoulos of the Massachusetts Institute of Technology (MIT).

Current waveguides require roughly a millimeter of turning radius to bend the 1.5-micron-wavelength light used in telecommunications by 90 degrees.

In the Oct. 9 Science, Shawn-Yu Lin of Sandia National Laboratories (SNL) in Albuquerque, N.M., and Joannopoulos and other MIT researchers describe bending millimeter-wavelength light through a right angle in just one wavelength. They expect the turning radius to remain one wavelength for shorter-wavelength light, saving considerable "real estate," they say.

The researchers accomplished their feat with a photonic crystal (SN: 11/16/96, p. 309)--a compact, orderly array of alumina posts, each about a millimeter apart, in which light travels only where lines of posts have been removed. Already built, they say, are much smaller crystals to be tested at the 1.5.-micron-wavelength