Giant field enhancement in longitudinal epsilon-near-zero films
Published Web Locationhttps://doi.org/10.1103/PhysRevB.95.161105
We report that a longitudinal epsilon-near-zero (LENZ) film leads to giant field enhancement and strong radiation emission of sources in it and these features are superior to what was found in previous studies related to isotropic ENZ. LENZ films are uniaxially anisotropic films where relative permittivity along the normal direction to the film is much smaller than unity, whereas the permittivity in the transverse plane of the film is not vanishing. It has been shown previously that realistic isotropic ENZ films do not provide large field enhancement due to material losses, however, we show the loss effects can be overcome using LENZ films. We also prove that, in comparison to the (isotropic) ENZ case, the LENZ film's field enhancement not only is remarkably larger, but also occurs for a wider range of angles of incidence. Importantly, the field enhancement near the interface of the LENZ film is almost independent of the thickness unlike what happens in the isotropic ENZ case where extremely small thickness is required. We show that, for a LENZ structure consisting of a multilayer of dysprosium-doped cadmium oxide and silicon accounting for realistic losses, field intensity enhancement of 30 is obtained which is almost ten times larger than that obtained with realistic ENZ materials.