Transmission enhancement in loss-gain multilayers by resonant suppression of reflection

TL;DR

This paper investigates how multilayer structures with loss and gain can achieve enhanced transmission and suppressed reflection through resonant effects, without requiring PT symmetry, using transfer-matrix and time-domain analysis.

Contribution

It introduces a novel mechanism for loss compensation and reflection suppression in multilayers that does not rely on PT symmetry, expanding the understanding of resonant transmission.

Findings

Resonant suppression of reflection enables enhanced transmission.

Reflectionless transmission occurs due to full loss compensation.

The mechanism applies to oblique and evanescent waves.

Abstract

Using the transfer-matrix approach and solving time-domain differential equations, we analyze the loss compensation mechanism in multilayer systems composed of an absorbing transparent conductive oxide and dielectric doped with an active material. We reveal also another regime with the possibility of enhanced transmission with suppressed reflection originating from the resonant properties of the multilayers. For obliquely incident and evanescent waves, such enhanced transmission under suppressed reflection turns into the reflectionless regime, which is similar to that observed in the PT-symmetric structures, but does not require PT symmetry. We infer that the reflectionless transmission is due to the full loss compensation at the resonant wavelengths of the multilayers.