Long-sojourning light in a photonic atoll

Very long photon lifetimes and resultant very high quality factors (Q-factors) are theoretically achieved in a system where microstructures are arranged periodically to make a closed chain loop. We call this a photonic-atoll resonator. The radiative Q-factor reaches an extremely high value in the vicinity of the edges of the light energy bands that could be regarded as the photonic bands created in the quasi-one-dimensional photonic crystal. This resonator is shown to have advantages over other resonators, e. g., a resonator using the defect mode localized in a regular photonic crystal.