The superprism phenomenon, the dispersion of light 500 times stronger than the dispersion in conventional prisms, was demonstrated at optical wavelengths in photonic crystals (PC's) fabricated on Si. Drastic light-beam steering in the PC's was achieved by slightly changing the incident wavelength or angle. The scanning span reached 50 with only a 1% shift of incident wavelength, and reached 140 with only a 14 shift of the incident angle at wavelengths around 1 m. The propagation direction was quantitatively interpreted in terms of highly anisotropic dispersion surfaces derived by photonic-band calculation. The physics behind this demonstration will open a novel field called photonic crystalline optics. The application of these phenomena promises to enable the fabrication of integrated microscale lightwave circuits (LC's) on Si with large scale integrated (LSI)-compatible lithography techniques. Such LC's will allow more efficient use of wavelength resources when used in wavelength multiplexers/demultiplexers or dispersion compensators by enabling lower loss and broader bandwidth.
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