Identification of the absorption processes in periodic plasmonic structures using energy absorption interferometry.

Area of Science:

• Electromagnetic theory
• Plasmonics
• Nanophotonics

Background:

• Power dissipation in electromagnetic absorbers depends quadratically on incident fields.
• Characterizing absorbers requires managing coupling between different excitations.
• Energy absorption interferometry (EAI) identifies independent energy absorption pathways (natural absorption modes).

Purpose of the Study:

• Analyze plasmonic periodic absorbers using EAI, rigorously accounting for mode coupling.
• Identify physical processes governing near- and far-field absorption.
• Exploit identified absorption channels to enhance absorber performance.

Main Methods:

• Application of the EAI formalism to resonant golden patches, silver wires, and silver slabs.
• Rigorous analysis of coupling effects between different absorption modes.
• Identification of dominant absorption channels through absorption mode signatures.

Main Results:

• Demonstrated limitations of classical angular absorption measurements under certain conditions.
• Identified dominant absorption channels by analyzing absorption modes with EAI.
• Showcased exploitation of long-range and short-range processes for enhanced spatial selectivity and wide-angle absorptivity.
• Achieved over a 10x increase in absorption by adding periodic scatterers.

Conclusions:

• EAI provides a rigorous framework for analyzing and understanding absorption mechanisms in plasmonic absorbers.
• The identified absorption channels offer pathways for designing highly efficient and selective absorbers.
• Simple modifications, like adding periodic scatterers, can dramatically improve absorber performance.