Topological phase transition in wire medium enables high Purcell factor at infrared frequencies

TL;DR

This paper investigates a topological phase transition in wire media at infrared frequencies, revealing a hybrid regime that significantly enhances radiation and yields a higher Purcell factor for axial dipoles compared to transverse ones.

Contribution

It introduces the concept of a hybrid topological regime in wire media at the transition frequency, leading to unprecedented radiation enhancement and higher Purcell factors for axial dipoles.

Findings

Hybrid regime exists at the transition frequency with touching surfaces.

Radiation enhancement is significantly higher for axial dipoles.

Purcell factor surpasses previous results for similar media.

Abstract

In this paper, we study topological phase transition in a wire medium operating at infrared frequencies. This transition occurs in the reciprocal space between the indefinite (open-surface) regime of the metamaterial to its dielectric (closed-surface) regime. Due to the spatial dispersion inherent to wire medium, a hybrid regime turns out to be possible at the transition frequency. Both such surfaces exist at the same frequency and touch one another. At this frequency, all values of the axial wavevector correspond to propagating spatial harmonics. The implication of this regime is the overwhelming radiation enhancement. We numerically investigated the gain in radiated power for a sub-wavelength dipole source submerged into such the medium. In contrast to all previous works, this gain (called the Purcell factor) turns out to be higher for an axial dipole than for a transversal one.