Coupling Strength and Total Damping Govern Electromagnetically Induced Absorption in Coupled Plasmonic Systems

Abstract

Electromagnetically induced absorption (EIA) is an optical phenomenon that enhances light absorption of plasmonic systems. Depending on the plasmonic system under investigation, the decisive role of intrinsic versus radiative damping and phase retardation has been pointed out to control the EIA. Herein, a unified interpretation is provided and the mechanism of EIA for plasmonic–dielectric composites and all‐plasmonic dipolar–quadrupolar antennas is unraveled. In this theoretical work, the finite element method is used to elucidate how EIA is attributed to an absorption enhancement of a resonance mode excited by near‐field coupling. For a fundamental understanding, a quantitative analysis is developed by designing an extended coupled‐oscillator model. A critical parameter to maximize EIA is found, which is different from previous interpretations of such coupled plasmonic systems. Namely, the ratio of coupling strength to the total damping of the entire system controls EIA. The generalized interpretation of EIA given by this work can be applied to many plasmonic systems and is essential for designing future optical components and devices.