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.

A plasmonic-photonic structure based on colloidal lithography was designed for a scalable radiative cooling system and its absorption properties were theoretically investigated. The structure comprises a SiO2 core, which is on top of an Au reflector and partially covered by an indium tin oxide (ITO) shell. This simple and scalable structure possesses a strong selective absorption in the primary atmospheric transparency window (8–13 µm). The strong selective absorption is attributed to a mode splitting of the localized surface plasmon (LSP) of the ITO shell. To understand the mechanisms of the mode splitting, a quantitative analysis was conducted using a coupled-oscillator model and a coupled-dipole method. The analysis revealed that the mode splitting is induced by a strong coupling between the LSP of the ITO shell and a magnetic dipole Mie resonance of the SiO2 core.

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A plasmonic broadband light absorber, whose absorption is insensitive to incident angles and polarizations, in the UV to near-infrared regions is demonstrated. In experimental observations, the maximum average absorption of 83% over a wavelength range from 300 to 1000 nm was confirmed. Our proposed plasmonic absorber is based on a three-layer stack of metal-insulator-metal, and the top metal layer is nanostructured by colloidal lithography. This structure is composed of Al, which is an excellent and cost-effective plasmonic material. This fabrication simplicity and economical material allows us to produce a large-scale device of solar absorbers.

Nano- and microstructures have been developed for asymmetric light transmission (ALT) filters operating in a wide wavelength range. One of the most straightforward structures with ALT properties is a dielectric corner reflector (DCR) comprising a one-dimensional grating of a triangular shape on one surface. The DCR possesses strong reflection only for one-way light illumination due to multiple total internal reflections (TIRs) inside the triangular grating. For triangular structures being much larger than the wavelength of light, the reflection properties are expected to be fully described by geometrical optics. However, geometrical optics do not account for the Goos–Hänchen (GH) shift, which is caused by the evanescent wave of the TIR. In this work, the reflection mechanism of DCRs is elucidated using the finite element method and a quantitative model built by considering the GH shift. The reduction in reflection of the DCR is dominated by diffraction of the evanescent wave at the corner of the triangular structure. Our model is based on simple mathematics and can optimize the DCR geometry for applications addressing a wide wavelength range such as radiative cooling.