Enhanced photonic band-gap confinement via Van Hove saddle point singularities |
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Authors: | Ibanescu Mihai Reed Evan J Joannopoulos J D |
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Affiliation: | Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239, USA. |
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Abstract: | We show that a saddle point Van Hove singularity in a band adjacent to a photonic crystal band gap can lead to situations which defy the conventional wisdom that the strongest band-gap confinement is found at frequencies near the midgap. As an example, we present a two-dimensional square photonic crystal waveguide where the strongest confinement is close to the band edge. The underlying mechanism can also apply to any system that is described by a band structure with a gap. In general, the saddle point favors the appearance of a very flat band, which in turn results in an enhanced confinement at band-gap frequencies immediately above or below the flat band. |
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