Self-collimating phenomena in photonic crystals

We found that self-determining collimated light is generated in a photonic crystal fabricated on silicon. The divergence of the collimated beam is ins ensitive to that of the incident beam and much smaller than the divergence that would be generated in conventional Gaussian optics. The incident-angle dependence of the self-collimated light propagation including lens-like di vergent propagation was interpreted in terms of the highly modulated disper sion surfaces with inflection points, where the curvature changes from down ward to upward corresponding to respectively a concave/convex-lens case. Th is demonstration is an important step towards controlling beam profile in p hotonic crystal integrated light circuits and towards developing "photonic crystalline optics.'' (C) 1999 American Institute of Physics. [S0003-6951(9 9)02809-0].