Inhibition and enhancement of the spontaneous emission in spherical cavities surrounded by zero-index-materials

There exist resonance degeneracy and nesting in the spherical dielectric cavity embedded in an infinite zero-index-material (ZIM). However, its spontaneous emission (SE) has been scarcely studied. Here, we investigate the inhibition and enhancement of SE in spherical dielectric cavities surrounded by ZIMs at the nanoscale. In the cavities embedded in ε-near-zero materials, by adjusting the polarization of the emitter, the SE of the emitter can be controlled from inhibition to enhancement, ranging from 10^-2 to dozens. For the cavities embedded in μ-near-zero or ε-μ-near-zero materials, the enhancement of SE is also achieved in a large range of cavities. These findings provide more application possibilities in single-photon sources, deformable optical devices with ZIMs, etc.