Superprism phenomena in photonic crystals: Toward microscale lightwave circuits

The superprism phenomenon, the dispersion of light 500 times stronger than the dispersion in conventional prisms, was demonstrated at optical waveleng ths in photonic crystals (PC's) fabricated on Si. Drastic light-beam steeri ng in the PC's was achieved by slightly changing the incident wavelength or angle, The scanning span reached 50 degrees with only a 1% shift of incide nt wavelength, and reached 140 degrees with only a 14 degrees shift of the incident angle at wavelengths around 1 mu m The propagation direction was q uantitatively interpreted in terms of highly anisotropic dispersion surface s derived by photonic-band calculation. The physics behind this demonstrati on will open a novel field called photonic crystalline optics. The applicat ion of these phenomena promises to enable the fabrication of integrated mic roscale lightwave circuits (mu LC's) on Si with large scale integrated (LSI )-compatible lithography techniques. Such mu LC's will allow more efficient use of wavelength resources when used in wavelength multiplexers/demultipl exers or dispersion compensators by enabling lower loss and broader bandwid th.