Extreme electromagnetic phenomena over an ultrathin platform




Kwon, Hoyeong

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Surrounded by tons of electromagnetic devices, understanding wave-matter interaction plays a pivotal role in modern technology. The in-depth understanding of the physics background, therefore, has promised improved functionalities of the current devices. Recently, the demand on novel technologies has required faster, smaller, and more efficient devices, requiring unprecedented phenomena exceeding the limits of nature. Interestingly, the advent of metamaterial provides the possibilities to meet these expectations, in which the material is engineered in deep subwavelength to manifest unusual phenomena. For the past decades, the potential of metamaterial has been proven with several demonstrations and experiments, providing new criteria of material properties. Especially, metasurfaces, the two-dimensional metamaterials, provide ultrathin platforms revealing novel properties. Supported by planar geometry, it can substitute the existing device, enhancing their functionalities or be the device itself. In this context, this dissertation focuses on metasurfaces achieving extreme phenomena and provides their practical implementations for various purposes. First, the study on light energy harvesting and broadband, omnidirectional light absorption have been performed. By abnormally guiding the light through a single metasurface, one can achieve the increased absorption efficiency under an absorptive layer by orders of magnitude. Also, by utilizing the Brewster effect, metasurfaces can control the spectrum and directivity of light absorption. Next, nonlocal metasurfaces are explored to perform ultrafast and low loss analog signal processing. Fano resonance provides a strong nonlocality in transverse momentum space, which supports different types of mathematical operations near the speed of light. Furthermore, nonlinear meta-structures are studied to manifest a second harmonic generation (SHG) effect from a concentric epsilon-near-zero (ENZ) material. The study shows that the plasmonic nanolayer of metal-insulator-metal structure can induce a strong SHG effect by coupling two different resonant modes within an ultrathin platform. At last, the concept of Parity-Time reversal (PT) symmetry is adopted to develop the noninvasive electromagnetic sensor. Here, I present the ultrathin active layer generating anisotropic transmission resonance (ATR) attached behind lossy media, where the resonance response that is dispersive with analytes provides improved sensitivity compared to the existing technology.


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