Abstract
We revisit the standard Nicolson–Ross–Weir method of effective permittivity and permeability restoration of photonic structures for the case of subwavelength metal-dielectric multilayers. We show that the direct application of the standard method yields a false zero-epsilon point and an associated spurious permeability resonance. We show how this artifact can be worked around by the use of the cycle shift operator to the periodic multilayer in question.
Highlights
Determining the effective macroscopic parameters of a slab containing a photonic structure is often both highly relevant both from a practical and from a fundamental point of view, providing a link between the actual microscopic composition of the structure and its macroscopic optical response
Applying the cycle shift operator effectively cycles through all possible terminations, and the best correspondence in parameter extraction happens when a good impedance matching between the multilayer and the outer space is achieved
We have demonstrated that the singularity in impedance originating from r = 1 and the zero value of its phase leads to artifacts in the retrieval of constitutive parameters of subwavelength photonic metal-dielectric multilayers, namely spurious magnetic resonance and a large mismatch of effective permittivity
Summary
Determining the effective macroscopic parameters of a slab containing a photonic structure is often both highly relevant both from a practical and from a fundamental point of view, providing a link between the actual microscopic composition of the structure and its macroscopic optical response. It is known that the constitutive parameters of a slab are hard to obtain nearby the total transmission frequency or when we approach the magnetic or electric resonances of a structure [5]. These difficulties can be overcome with a modified extraction procedure, based upon a generalized homogenization technique [6]. Being able to make a correction for artifacts in such a regime becomes of particular importance to determine the correct operational wavelengths of epsilon-near-zero behavior and the optical mechanism of subwavelength photonic structures.
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