We report analytical and numerical studies of the effect of the separation distance between zeros of dielectric permittivity and magnetic permeability on the phenomena of resonant absorption and anomalous field enhancement in transition metamaterials. Our studies indicate that these phenomena are robust and strongly polarization-dependent in the presence of the spatial shift between these points. These results are likely to be important for future fundamental and applied studies in the areas of transformation, polarization, and nonlinear optics in metamaterials.
[Show abstract][Hide abstract] ABSTRACT: We theoretically and numerically investigate the phenomenon of resonant field
enhancement of Gaussian beams in two types of transition metamaterials: with a
positive-zero-negative index profile and with a positive-zero-positive index
profile and demonstrate strongly localized resonant field enhancement in both
cases. This study is likely to have applications in the fields of nano-optics,
sub-wavelength imaging, and nano-fabrication and lays a foundation for the
studies of more complex vector and vortex beam propagation in graded-index
[Show abstract][Hide abstract] ABSTRACT: Anomalous optical coupling properties between two silicon wires in a silicon
slot waveguide embedded in epsilon-near-zero (ENZ) metamaterials are proposed
and demonstrated. The dependences of optical field enhancement in the slot
region and transverse optical force on the slot size and the permittivity of
surrounding material are studied in details. It is demonstrated that the
optical field in the slot region is significantly enhanced due to the giant
index contrast at the slot interface between silicon wires and ENZ
metamaterials, but the optical mode coupling between silicon wires is greatly
reduced so that the transverse optical force is suppressed into almost zero.
Moreover, metal-dielectric multilayer structures are designed to realize ENZ
metamaterials in the slot region for achieving the electric field enhancement.
[Show abstract][Hide abstract] ABSTRACT: Materials with negative permittivity and permeability can overcome the diffraction limit, thereby making the sub-wavelength imaging possible. In this study, we analyze the effects of gradient index on a half-infinite perfect lens. We assume that the sharp interface between the vacuum and the negative-index material is replaced by a smooth transition profile such that the index gradually changing from positive to negative. Interestingly, we find that if the graded index profile is modeled by a tanh function, we can have closed-form analytical solutions for this problem, which is a distinct advantage as numerical solutions are not accurate for evanescent waves with large transverse wave vectors. By analyzing the analytical formulas we confirm that a nonzero total absorption can occur even for a near-zero absorption coefficient in the steady-state limit and the image plane contains multiple sub-wavelength images of an object.
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