Fabry-Perot Microcavity with Epsilon-Near-Zero (ENZ) Spacer: Wavelength-Scale Electromagnetic Analysis

We performed electromagnetic analysis of a Fabry-Perot microcavity with metallic mirrors and a spacer with epsilon-near-zero (ENZ) permittivity material. We observed an enormously strong electric field amplitude localisation within the microcavity at its maximal transmission. As the permittivity of the spacer approached zero while maintaining its positive value, the amplitude of the electric field continued to enhance. The strong localisation of the electric field is favourable for efficient realization of loss, gain and non-linearity in the Fabry-Perot microcavity with ENZ spacer. We employed the method of single expression (MSE) for such wavelength-scale electromagnetic analysis. The optical microstructure presented in this work holds promise for nanophotonic applications, including use as a thin-film absorber or amplifier, an optical switch, or a compact optical modulator.