Enhanced Spontaneous Emission at Third-Order Dirac Exceptional Points in Inverse-Designed Photonic Crystals

• Published in: Physical review letters Vol. 117; no. 10; p. 107402
• Main Authors: Lin, Zin, Pick, Adi, Lončar, Marko, Rodriguez, Alejandro W
• Format: Journal Article
• Language: English
• Published: United States 02-09-2016
• Subjects: Coalescing; Computation; Density of states; Emitters; Photonic crystals; Spectra; Spontaneous emission; Topology optimization
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/physrevlett.117.107402

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 ∼sqrt[n^{3}] possible at exceptional points of higher order n.