Recently, the so-called perfect absorbers, which are light-trapping nanostructures absorbing almost 100% of incident light with a designed wavelength, have attracted significant attention. The perfect absorbers consist of multilayers (absorption, dielectric, and mirror layers), which can be theoretically realized by any combination of materials. However, in order to achieve properties useful for a specific purpose, it is necessary to tune the optical properties of the absorption and dielectric layers by introducing metamaterials into the layered structures. Oblique-angle deposition (OAD) is one of the most powerful techniques to tailor metamaterials, which include well-controlled nanomorphologies significantly smaller than the wavelength of visible light, enabling the control of optical properties of various materials in different wavelength regions, from ultraviolet to infrared, at low costs. In this paper, we present several types of perfect absorbers fabricated by the OAD technique and their applications to photocatalysts, biochemical sensors, optical elements, and thermoplasmonic control of microfluidics.
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