Abstract
Recently, it was noted that losses in plasmonics can also enable several useful optical functionalities. One class of structures that can maximize absorption are metal insulator metal systems. Here, we study 3-layer systems with a nano-composite metal layer as top layer. These systems can absorb almost 100% of light at visible frequencies, even though they contain only dielectrics and highly reflecting metals. We elucidate the underlying physical phenomenon that leads to this extraordinary high and broadband absorption. A comprehensive study of the particle material and shape, mirror material and dielectric spacer thickness is provided to identify their influence on the overall absorption. Thus, we can provide detailed design guidelines for realizing optical functionalities that require near-perfect absorption over specific wavelength bands. Our results reveal the strong role of lossy Fabry-Perot interference within these systems despite their thickness being well below half a wavelength.
Highlights
Losses associated with plasmonics were seen as detrimental; it was recently noted that losses can enable several useful optical functionalities and are related to strong local field enhancements [1]
A comprehensive study of the particle material and shape, mirror material and dielectric spacer thickness is provided to identify their influence on the overall absorption
We have investigated numerically the optical response of metal insulator metal (MIM) systems with a top nanocomposite layer and different mirror materials, particle materials and dielectric spacer thicknesses
Summary
Losses associated with plasmonics were seen as detrimental; it was recently noted that losses can enable several useful optical functionalities and are related to strong local field enhancements [1]. One particular class of structures that can maximize absorption in the visible spectrum (VIS) are metal insulator metal (MIM) systems [5] Such 3-layer systems consist typically of a metallic base layer (mirror layer), a dielectric spacer layer and an at least partially metallic top layer. Several well-ordered and defined MIMs have been manufactured [7,8,9,10,11,12,13,14] They have typically periodic top layers and can achieve broad-band absorption levels in the range of 6080% for the case of thoroughly optimized systems [7], while certain systems can even absorb up to 100% in the infrared spectrum [8]. The top layer contains randomly sized and arranged metal nano particles that are usually embedded in a dielectric matrix (in this article we will call such a layer a nano-composite layer)
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