Simultaneous Realization of Coherent Perfect Absorber and Laser by Zero-Index Media with both Gain and Loss

TL;DR

This paper demonstrates that a zero-index medium with both gain and loss can simultaneously function as a coherent perfect absorber and laser, offering a novel approach distinct from PT-symmetric systems, confirmed through analytical and numerical methods.

Contribution

It introduces a new zero-index medium with gain and loss for simultaneous CPA and laser, differing from PT-symmetric systems, and realizes it using a designed photonic crystal.

Findings

Analytical proof of CPA-laser in ZIM-GL

Design and realization of ZIM-GL in photonic crystal

Numerical confirmation of CPA-laser functionality

Abstract

We investigate a unique type of zero-index medium with both gain and loss (ZIMGL), whose effective permittivity and permeability are purely imaginary and of opposite signs. We show analytically that, by using a slab of ZIM-GL with equal magnitude of loss and gain, coherent perfect absorber (CPA) and laser, i.e. the socalled CPA-laser, can be achieved simultaneously. CPA-laser has been found previously in parity-time (PT) symmetric systems. However, the underlying physics in a PT-symmetric system is distinct from that in a ZIM-GL. By designing a photonic crystal (PC) composed of core-shell rods, with loss and gain distributed in either the core or the shell, we have realized such a ZIM-GL. The CPA-laser functionality of such a PC is also confirmed in our numerical simulations. Our work provides a different approach for simultaneous realization of CPA and laser besides PTsymmetric systems.