Simultaneous realization of a coherent perfect absorber and laser by zero-index media with both gain and loss

Abstract

We investigate a unique type of zero-index medium with both gain and loss (ZIMGL), whose effective permittivity and permeability are both purely imaginary but of opposite signs. We analytically show that, by using a slab of ZIMGL with equal magnitude of loss and gain, simulation realization of a coherent perfect absorber (CPA) and laser, i.e., the so-called CPA laser, can be achieved. Previously the CPA laser was proposed in parity-time (P T ) symmetric systems. However, the ZIMGL does not possess the P T symmetry and thus the underlying physics is distinctly different. 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 ZIMGL. 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 P T -symmetric systems.

Electromagnetic Impurity-Immunity Induced by Parity-Time Symmetry

“…In addition, subwavelength structures with a large amount of gain can be realized by using multilayered structures [48], microwave and optical metastructures with gain [71][72][73][74][75], etc. In particular, the effective gain media with pure permittivity or permeability have also been demonstrated in core-shell composites [76]. These works manifest the possibility of realizing the metasurfaces with the required effective gain parameters.…”

Coherent perfect absorber and laser modes in purely imaginary metamaterials

“…In addition, the general conditions for realizing CPA and laser modes have been derived. We also identify the conditions for realizing CPA mode and laser mode simultaneously, with the case of normal incidence [22][23][24] as a special case. More interestingly, as a simplification of CPA modes, single-sided PA modes can be obtained in a PICM slab with a sub-unity effective index for the incident angle beyond the critical angle.…”

“…By employing PT-symmetric materials in layered structures [23], PICMs can be effectively mimicked, with the similar CPA-laser effect realized. The other method is that, based on the effective medium theory [25], PICMs could be well designed by using a photonic crystal composed of core-shell rods [24], in which loss and gain media are distributed in either the cores or the shells. Therefore, considering the recent experimental progress in optical gain [17], PICMs might be realized experimentally in the coming future.…”

Coherent Perfect Absorption via Photonic Doping of Zero‐Index Media

“…Perfect absorption of electromagnetic wave energy is a fundamental physical issue with wide applications in sensing and molecular detection, radar detection, photovoltaics, nanophotonics, etc. Recently, the concept of coherent perfect absorption (CPA), as time‐reversed lasing, has been proposed and attracted a lot of research interest . In the standard scheme of CPA, perfect absorption of electromagnetic energy is achieved via the interference of two counter‐propagating incident plane waves in a thin film absorber.…”