Giant enhancement of reflectance due to the interplay between surface confined wave modes and nonlinear gain in dielectric media

TL;DR

This paper theoretically investigates how surface confined wave modes and both linear and nonlinear gain in dielectric media can dramatically enhance reflectance, revealing multistability and giant amplification effects with potential applications in thermal control.

Contribution

It introduces a comprehensive analysis of the interplay between surface wave modes and gain in dielectric layers, highlighting conditions for giant reflectance enhancement and multistability.

Findings

Large reflectance peaks exceeding 1 due to gain-mode interplay

Multistability and complex topological changes in reflectance curves

Giant reflectance amplification by three orders of magnitude near waveguide modes

Abstract

We study theoretically the interplay between the surface confined wave modes and the linear and nonlinear gain of the dielectric layer in the Otto configuration. The surface confined wave modes such as surface plasmons or waveguide modes are excited in the dielectric-metal bilayer by obliquely incident $p$ waves. In the purely linear case, we find that the interplay between linear gain and surface confined wave modes can generate a large reflectance peak with its value much greater than 1. As the linear gain parameter increases, the peak appears at smaller incident angles, and the associated modes also change from surface plasmons to waveguide modes. When the nonlinear gain is turned on, the reflectance shows very strong multistability near the incident angles associated with surface confined wave modes. As the nonlinear gain parameter is varied, the reflectance curve undergoes complicated topological changes and sometimes displays separated closed curves. When the nonlinear gain parameter takes an optimally small value, a giant amplification of the reflectance by three orders of magnitude occurs near the incident angle associated with a waveguide mode. We also find that there exists a range of the incident angle where the wave is dissipated rather than amplified even in the presence of gain. We suggest that this can provide the basis for a possible new technology for thermal control in the subwavelength scale.