Abstract
In this work, we study the effect of spatial dispersion on propagation properties of planar waveguides with the core layer formed by hyperbolic metamaterial (HMM). In our case, the influence of spatial dispersion was controlled by changing the unit cell’s dimensions. Our analysis revealed a number of new effects arising in the considered waveguides, which cannot be predicted with the help of local approximation, including mode degeneration (existence of additional branch of TE and TM high-β modes), power flow inversion, propagation gap, and plasmonic-like modes characterized with long distance propagation. Additionally, for the first time we reported unusual characteristic points appearing for the high-β TM mode of each order corresponding to a single waveguide width for which power flow tends to zero and mode stopping occurs.
Highlights
Propagation Properties ofBy utilizing nanostructurization at the subwavelength scale, optical metamaterials provide a means for controlling light propagation that is not available in conventional media [1,2,3,4]
In the course of the analysis, we demonstrated a number of new effects arising in the presence of spatial dispersion, including mode degeneracy leading to occurrence of an additional branch of TE/transverse magnetic (TM) modes characterized with a high propagation constant and high modal confinement
Within the scope of our analysis, we considered a symmetric hyperbolic metamaterial (HMM) waveguide cladded with air (ε air ≈ 1)
Summary
By utilizing nanostructurization at the subwavelength scale, optical metamaterials provide a means for controlling light propagation that is not available in conventional media [1,2,3,4]. More recent studies reported substantial deviations between the electromagnetic response predicted with the help of the local EMT and the actual behavior of realistic nanostructures [23,24,25,26] The origin of these discrepancies has been identified as the influence of spatial dispersion, which can be described as the wavevector-dependence of permittivity, which may cause the occurrence of an additional optical axis [27]. The presented results revealed that spatial dispersion substantially influences propagation properties of waveguides based on HMM and may lead to new effects that cannot be predicted with the help of local approximation
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