Let There be No Light; February 1998; Scientific American Magazine; by Hayashi; 1 Page(s)
Semiconductors have an extremely useful feature: electrons in those materials can exist only at certain energy levels that are separated by forbidden territory called an electronic bandgap. Tinkering with this property enables engineers to tailor the electrical characteristics of transistors made from silicon and other semiconductors and hence optimize them for use in computer chips. Materials with a comparable property with respect to light--that is, a substance with a "photonic bandgap"-- might prove similarly useful. During the past several years, researchers have made such devices that worked at microwave frequencies. But now scientists at the Massachusetts Institute of Technology have succeeded in fabricating a structure that definitively works at nearvisible light, paving the way for possible uses in lasers, fiber-optic communications and other applications.
The M.I.T. structure is deceptively simple: it¿s basically a tiny ridge of silicon with microscopic holes drilled in a row along the strip¿s length. The key, though, is that the holes are spaced at a regular interval that is on the same scale as the wavelength of visible light-- that is, less than a millionth of a meter. At such dimensions, the holes block light traveling through the ridge; a tighter spacing of the holes would block light of even shorter wavelengths.