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Register a new userTri- & Tetra-Hyperbolic Iso-frequncy Topologies Complete Classification of Bi-Anisotropic Materials
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We describe novel topological phases of iso-frequency k-space surfaces in bi-anisotropic optical materials - tri- and tetra-hyperbolic materials, which are induced by introduction of chirality. This completes the classification of iso-frequency topologies for bi-anisotropic materials, since as we show all optical materials belong to one of the following topological classes: tetra-, tri-, bi-, mono- or non-hyperbolic. We show that phase transitions between these classes occur in the k-space directions with zero group velocity at high k-vectors. This classification is based on the sets of high-k polaritons (HKPs), supported by materials. We obtain the equation describing these sets and characterize the longitudinal polarization impedance of HKPs.
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In this paper we reveal the physics behind the formation of tri- and tetra-hyperbolic phases in anisotropic metamaterials without magnetoelectric coupling and describe the anti-crossing splitting phenomenon in the hyperbolic dispersion which arises due to the hybridization of the plasmonic and magnetic Bloch high-k polaritons. This considerably deepens the understanding of the high-k polaritons and the topology of the optical iso-frequency surfaces in k-space and will find applications in optical nano-resolution imaging and emission rate and directivity control. To accomplish this, we develop a range of new techniques of theoretical optics for bianisotropic materials, including the quadratic index of refraction operator method, suitable to study the high-k polaritons with finite indices of refraction and the explicit expression for the characteristic matrix in generic bianisotropic media. We introduce the spatial stratification approach for the electric and magnetic responses of anisotropic homogeneous media to analyze the underlying Bloch waves. We believe that the formalisms developed here can be useful for the researchers in the field of theoretical optics of anisotropic and bianisotropic media in the future.
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We theoretically demonstrate the fundamental limit in volume for given materials (e.g. Si, a-Si, CdTe) to fully absorb the solar radiation above bandgap, which we refer as solar superabsorption limit. We also point out the general principles for experimentally designing light trapping structures to approach the superabsorption. This study builds upon an intuitive model, coupled leaky mode theory (CLMT), for the analysis of light absorption in nanostructures. The CLMT provides a useful variable transformation. Unlike the existing methods that rely on information of physical features (e.g. morphology, dimensionality) to analyze light absorption, the CLMT can evaluate light absorption in given materials with only two variables, the radiative loss and the resonant wavelength, of leaky modes, regardless the physical features of the materials. This transformation allows for surveying the entire variable space to find out the solar superabsorption and provides physical insights to guide the design of solar superabsorbing structures.
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