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 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 μm. 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 (μLC's) on Si with large scale integrated (LSI)-compatible lithography techniques. Such μLC'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.