Abstract
In this article, we use a versatile homogenization approach to model the linear and nonlinear optical response of two metasurfaces: a plasmonic metasurface consisting of graphene patches and a dielectric photonic nanostructure consisting of silicon photonic crystal (PhC) cavities. The former metasurface is resonant at wavelengths that are much larger than the graphene elements of the metasurface, whereas the resonance wavelengths of the latter one are comparable to the size of its resonant components. By computing and comparing the effective permittivities and nonlinear susceptibilities of the two metasurfaces, we infer some general principles regarding the conditions under which homogenization methods of metallic and dielectric metasurfaces are valid. In particular, we show that in the case of the graphene metasurface the homogenization method describes very well both its linear and nonlinear optical properties, whereas in the case of the silicon photonic nanostructure the homogenization method is only qualitatively accurate, especially near the optical resonances.
Highlights
INTRODUCTIONMetamaterials, whose emergence has opened up exciting new opportunities to create novel media with pre-designed physical properties, have been proving to have a significant impact on the development of new approaches and devices for controlling light interaction with matter and achieving key functionalities, including light focusing [1]–[3], perfect lensing [4], [5], perfect absorption [6]–[10], electromagnetic cloaking [11]–[13], imaging with sub-diffraction resolution [14]–[18], and optical sensing [19]–[22]
AND DISCUSSIONS we study the circumstances in which our method produces accurate results and use it to understand the main differences between the physical properties of graphene and silicon photonic crystal (PhC) metasurfaces
In summary, two generic metasurfaces, a graphene metasurface based on graphene cruciform patches and a silicon photonic nanostructure with photonic crystal cavities as building blocks, are studied using a versatile and powerful homogenization method
Summary
Metamaterials, whose emergence has opened up exciting new opportunities to create novel media with pre-designed physical properties, have been proving to have a significant impact on the development of new approaches and devices for controlling light interaction with matter and achieving key functionalities, including light focusing [1]–[3], perfect lensing [4], [5], perfect absorption [6]–[10], electromagnetic cloaking [11]–[13], imaging with sub-diffraction resolution [14]–[18], and optical sensing [19]–[22]. As research in metamaterials advanced, it became clear that the two-dimensional (2D) counterpart of metamaterials, the so-called metasurfaces, would offer the fastest route to functional devices and applications This is so because most nanofabrication techniques can conveniently be applied to the planar configuration of metasurfaces. Important from a practical perspective, the single-layer characteristics of photonic devices based on metasurfaces make them amenable to system integration Because of their small thickness, light-matter interaction occurs in a reduced volume and as such optical losses in metasurfaces are relatively small. Dielectric metasurfaces, on the other hand, experience much smaller optical losses but only provide limited optical field enhancement Another difference between the two classes of metasurfaces, which is directly related to the magnitude of the optical losses, is that whereas the resonances in the plasmonic metasurfaces are relatively broad, the resonances associated to dielectric metasurfaces are narrow. We conclude our paper by summarizing the main findings of our study and discussing some of their implications to future developments pertaining to metamaterials research
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