Fig. 10
From: Spontaneous emission in micro- or nanophotonic structures
a Sketch of air cavity embedded in the open ENZ materials with nonradiating and radiating modes [354]. b Purcell factors for different amounts of loss (ε′′) in the ENZ medium in structure (a) [354]. c Sketch of optical cavity made of zero-index metamaterial [337]. d Purcell factor of directional single photon source in structure (c) [337]