Splitting of triply degenerate refractive indices by photonic crystals

Hideo Kosaka, Akihisa Tomita, Takayuki Kawashima, Takashi Sato, Shojiro Kawakami

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


The refractive index is inherently triply degenerate in conventional crystals, but this degeneracy is lifted and the refractive index is split into a phase, a group, and a “fan” index by photonic crystals. These indices are explained as three different sections passing through the photonic band structure. We observed the fan index, which describes beam divergence and is defined by the local curvature of the equienergy section, range from near zero to almost infinity. This paper provides a unified description of photonic and conventional crystal optics, and may enable previously inconceivable optical designs.

Original languageEnglish
Pages (from-to)1477-1480
Number of pages4
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number3
Publication statusPublished - 2000 Jan 1

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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