Multi-Functional Metal-Dielectric Photonic Structures. (2016) - Dissertation

One dimensional photonic structures with defects made to the periodicity showcase interesting localization effects in the energy distribution, specifically with high transmission for a given frequency. When a normally non-transmissive metallic layer is considered, no transmission could occur, but when such a layer is placed at the location of this defect, transmission can occur. Furthermore, due to the unique energy distribution, such a composite structure can enable large magnetic properties that would otherwise not be used due to high reflective or absorptive properties of the original magnetic layer. This work was done within the microwave and RF ranges, however principally works for all frequencies with the appropriate size and choice of materials.

Hypersensitive transport in photonic crystals with accidental spatial degeneracies (2016)

A localized mode in a photonic layered structure can develop nodal points (nodal planes), where the oscillating electric field is negligible. Placing a thin metallic layer at such a nodal point results in the phenomenon of induced transmission. Here we demonstrate that if the nodal point is not a point of symmetry, then even a tiny alteration of the permittivity in the vicinity of the metallic layer drastically suppresses the localized mode along with the resonant transmission. This renders the layered structure highly reflective within a broad frequency range. Applications of this hypersensitive transport for optical and microwave limiting and switching are discussed.

Enhanced transmission and giant Faraday effect in magnetic metal–dielectric photonic structures (2013)

Due to their large electrical conductivity, stand-alone metallic films are highly reflective at microwave (MW) frequencies. For this reason, it is nearly impossible to observe Faraday rotation in ferromagnetic metal layers, even in films just tens of nanometers thick. Here, we show using numerical simulations that a stack of cobalt nano-layers interlaced between dielectric layers can become highly transmissive and display a large Faraday rotation in a finite frequency band. A 45 Faraday rotation commonly used in MW isolators can be achieved with ferromagnetic metallic layers as thin as tens of nanometers.

Enhanced transmission and nonreciprocal properties of a ferromagnetic metal layer in one-dimensional photonic crystals (2011)

We show in transfer-matrix calculations of electromagnetic transmission through a ferromagnetic metal layer embedded in one-dimensional photonic crystals that electromagnetic losses can be greatly suppressed and nonreciprocal response significantly enhanced, when placing the layer at the node of the localized mode produced at the defect in the periodic structure. Nonreciprocal circular dichroism and Faraday rotation are observed at the ferromagnetic resonance and far from the resonance, respectively, and can be controlled with magnetic field.

Modeling of plastic deformation effects in ferromagnetic thin films (2010)

To explain the magnetic behavior of plastic deformation of thin magnetic films (Fe and permalloy) on an elastic substrate (nitinol), it is noted that unlike in the bulk, the dislocation density does not increase dramatically because of the dimensional constraint. As a result, the resulting residual stress, even though strain hardening is limited, dominates the observed magnetic behavior. Thus, with the field parallel to the stress axis, the compressive residual stress resulting from plastic deformation causes a decrease in remanence and an increase in coercivity; and with the field perpendicular to the stress axis, the resulting compressive residual stress causes an increase in remanence and a decrease in coercivity. These elements have been inserted into the model previously developed for plastic deformation in the bulk, producing the aforementioned behavior, which has been observed experimentally in the films.