Publications

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This work describes controlling light propagation, emission and topological behavior of light using seminconductor based nanophotonic structures.

Geomagnetic disturbances (GMDs) give rise to geomagnetically induced currents (GICs) on the earth's surface which find their way into power systems via grounded transformer neutrals. The quasi-dc nature of the GICs results in half-cycle saturation of the power grid transformers which in turn results in transformer failure, life reduction, and other adverse effects. Therefore, transformers need to be more resilient to dc excitation. This paper sets forth dc immunity metrics for transformers. Furthermore, this paper sets forth a novel transformer architecture and a design methodology which employs the dc immunity metrics to make it more resilient to dc excitation. This is demonstrated using a time-stepping 2D finite element analysis (FEA) simulation. It was found that a relatively small change in the core geometry significantly increases transformer resiliency with respect to dc excitation.

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Here, we review the progress and most recent advances in phonon-polaritonics, an emerging and growing field that has brought about a range of powerful possibilities for mid- to far-infrared (IR) light. These extraordinary capabilities are enabled by the resonant coupling between the impinging light and the vibrations of the material lattice, known as phonon-polaritons (PhPs). These PhPs yield a characteristic optical response in certain materials, occurring within an IR spectral window known as the reststrahlen band. In particular, these materials transition in the reststrahlen band from a high refractive-index behavior, to a near-perfect metal behavior, to a plasmonic behavior - typical of metals at optical frequencies. When anisotropic they may also possess unconventional photonic constitutive properties thought of as possible only with metamaterials. The recent surge in two-dimensional (2D) material research has also enabled PhP responses with atomically-thin materials. Such vast and extraordinary photonic responses can be utilized for a plethora of unusual effects for IR light. Examples include sub-diffraction surface wave guiding, artificial magnetism, exotic photonic dispersions, thermal emission enhancement, perfect absorption and enhanced near-field heat transfer. Finally, we discuss the tremendous potential impact of these IR functionalities for the advancement of IR sources and sensors, as well as for thermal management and THz-diagnostic imaging.

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We demonstrate a top-down fabrication strategy for creating a III-nitride hole array photonic crystal (PhC) with embedded quantum wells (QWs). Our photoelectrochemical (PEC) etching technique is highly bandgap selective, permitting the removal of QWs with well-defined indium (In) concentration. Room-temperature micro-photoluminescence (μ-PL) measurements confirm the removal of one multiple quantum well (MQW) while preserving a QW of differing In concentration. Moreover, PhC cavity resonances, wholly unobservable before, are present following PEC etching. Our results indicate an interesting route for creating III-nitride membranes with tailorable emission wavelengths. Our top-down fabrication approach offers exciting opportunities for III-nitride based light emitters.

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