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Perfectly Absorbing Exceptional Points and Chiral Absorbers
William R Sweeney1, Chia Wei Hsu2, Stefan Rotter3
1Department of Physics, Yale University, New Haven, Connecticut 06520, USA.
Physical Review Letters
|April 2, 2019
Summary
Researchers discovered a new type of exceptional point (EP) enabling perfect absorption of waves. This phenomenon, observed in electromagnetic and acoustic systems, allows for chiral absorption in resonators, absorbing waves rotating in only one direction.
Area of Science:
- Physics
- Wave Phenomena
- Non-Hermitian Systems
Background:
- Exceptional points (EPs) are degeneracies in non-Hermitian systems, often associated with lasers.
- Previous EPs typically require noise or nonlinearity and do not directly relate to absorption.
Purpose of the Study:
- To identify and characterize a new class of physically realizable exceptional points (EPs).
- To explore the connection between EPs and coherent perfect absorption in wave systems.
- To investigate the properties of these EPs in electromagnetic and acoustic wave operators.
Main Methods:
- Analysis of wave operator solutions for electromagnetic and acoustic waves.
- Investigation of non-Hermitian degeneracies at real-valued frequencies.
- Characterization of absorption line shapes and scattering matrices near EPs.
Main Results:
- Identified a novel EP corresponding to degenerate coherent perfect absorption.
- Demonstrated that these EPs can occur without noise or nonlinearity.
- Observed a quartic absorption line shape near the EP in any dimension.
- Found that in one dimension, a perfectly absorbing EP in the S-matrix has a universal one-parameter form.
- Discovered chiral absorption in absorbing disk resonators due to these EPs.
Conclusions:
- A new, physically realizable EP related to coherent perfect absorption has been identified.
- These EPs offer a distinct mechanism for wave absorption, differing from laser-related EPs.
- The phenomenon leads to unique properties like chiral absorption, with potential applications in wave manipulation.
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