Abstract: An optical waveguide including: a dielectric core region extending along a waveguide axis; and a dielectric confinement region surrounding the core about the waveguide axis, the confinement region comprising a photonic crystal structure having a photonic band gap, wherein during operation the confinement region guides EM radiation in at least a first range of frequencies to propagate along the waveguide axis, wherein the core has an average refractive index smaller than about 1.3 for a frequency in the first range of frequencies, and wherein the core a diameter in a range between about 4&lgr; and 80&lgr;, wherein &lgr; is a wavelength corresponding to a central frequency in the first frequency range.

Abstract: A method for converting electromagnetic (EM) energy between guided modes of a photonic crystal waveguide having a waveguide axis, the method including: (i) providing the photonic crystal waveguide with a mode coupling segment comprising at least one bend in the waveguide axis, wherein during operation the mode coupling segment converts EM energy in a first guided mode to a second guided mode; (ii) providing EM energy in the first guided mode of the photonic crystal waveguide; and (iii) allowing the EM energy in the first guided mode to encounter the mode coupling segment to convert at least some of the EM energy in the first guided mode to EM energy in the second guided mode.