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Lin, Zin; Pick, Adi; Lončar, Marko; Rodriguez, Alejandro W
Physical review letters, 2016-Sep-02, Letnik: 117, Številka: 10Journal Article
We formulate and exploit a computational inverse-design method based on topology optimization to demonstrate photonic crystal structures supporting complex spectral degeneracies. In particular, we discover photonic crystals exhibiting third-order Dirac points formed by the accidental degeneracy of monopolar, dipolar, and quadrupolar modes. We show that, under suitable conditions, these modes can coalesce and form a third-order exceptional point, leading to strong modifications in the spontaneous emission (SE) of emitters, related to the local density of states. We find that SE can be enhanced by a factor of 8 in passive structures, with larger enhancements ∼sqrtn^{3} possible at exceptional points of higher order n.
