Coherent perfect absorption of anti-modes in an indirect coupled magnon-polariton system

TL;DR

This paper demonstrates coherent perfect absorption of anti-modes in an indirectly coupled magnon-polariton system, showing tunable, frequency-selective microwave absorption with potential reconfigurability.

Contribution

It introduces the experimental observation of CPA in an indirect magnon-polariton coupling, distinguishing modal decay from effective decay, and demonstrates broad, tunable absorption.

Findings

CPA causes zero effective decay rate and narrow spectrum

Effective decay rate influences spectral amplitude, not physical loss

CPA is tunable over a broad magnetic detuning range

Abstract

In this work, we report coherent perfect absorption (CPA) of anti-modes in an indirectly coupled magnon--polariton system. By examining both single and indirectly coupled cases, we experimentally distinguish the modal decay rate $\gamma$ from the effective decay rate $\gamma_{\rm{eff}}$. At CPA, $\gamma_{\rm{eff}} = 0$, leading to a vanishing output and a visually narrow spectrum in the dB-scale, while the intrinsic linewidth set by $2\gamma$ remains unchanged, demonstrating that the effective decay rate dictates the spectral amplitude rather than the physical loss. Furthermore, in the indirectly coupled system, CPA persists over a broad, magnetically tunable detuning range, in contrast to the single-detuning CPA observed in the directly coupled case, thereby enabling magnetically reconfigurable and frequency-selective microwave absorbers.