Giant Field Enhancement in Longitudinal Epsilon Near Zero Films

TL;DR

This paper demonstrates that longitudinal epsilon-near-zero (LENZ) films can achieve significantly larger and more robust electromagnetic field enhancements compared to isotropic ENZ films, even with realistic material losses.

Contribution

The study introduces the concept of LENZ films with uniaxial anisotropy, showing they outperform isotropic ENZ films in field enhancement and radiation emission, overcoming material loss limitations.

Findings

LENZ films produce larger field enhancements than isotropic ENZ.

Field enhancement in LENZ is less sensitive to film thickness.

Realistic LENZ multilayers achieve 30-fold field intensity enhancement.

Abstract

We report that a longitudinal epsilon-near-zero (LENZ) film leads to giant field enhancement and strong radiation emission of sources in it and that these features are superior to what 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, while 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 field enhancement is not only remarkably larger but it 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 for 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 10 times larger than that obtained with realistic ENZ materials