Analysis and Computation of Polaritonic Systems in Infrared Regime for Sensing Applications
Alsalhin, Abdelgader Ahmed Alshiekh
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Generally, the aims of this work tend to focus on introducing novel designs for IR-sensing and a solid related knowledge based on computational analysis and investigations for polaritonic systems. This modern field of nanophotonics has been interested and promising nowadays thanks to the development in nano-fabrications and computing power and speed. Therefore, the theme-work is organized into two main parts along with the goals were addressed initially. The first part provides the necessary concepts for different responses of materials exposed to electromagnetic (EM) intensity which usually known as EM-matter interaction. Also, this part highlights how engineering these interactions in nano-scale could be exploited, where the irregular responses in that scale offer new possible functions. First two chapters present this part. Subsequently, the second part starts with showing how those concepts are correlated to design-considerations through some well-known computational methods like FEM, EM scattering theory, EMT, and TMM. All these listed methods will be devoted directly or indirectly for bunch of investigations and designs related to sensing applications. Starting with a study suggested a novel design for IR-sensing based on the coupling between metallic structure (gold [Au], graphene [C]) and phonon polariton (hexagonal boron nitride [hBN]) where it was published as a conference paper. Another novel published contribution is regarding to a new suggestion of hybrid technique to determine the dispersive feature for any polaritonic structure in IR regime. This technique merged between two mature methods (FEM, and TMM) and leverages their advantages. The hybrid technique was implemented to determine the dispersions of a slab of hBN type-II for the sake of benchmarking where the results were compatible with related literature. In addition, a co-research combines the idea of sensing and imaging in IR regime was introduce and published. By modifying a structure used to work in visible light, a novel IR-metalense design was implemented using semiconductors (doped and undoped InAs) to provide a hot spot at the surface. This lens shows a great diffraction limit that qualifies it for imaging objects 1000-times smaller than the wavelength. Finally, extensional work for the sensing-structure (Au, hBN) has been presented to be a journal paper. In this study, the hybrid (FEM/TMM) technique is applied to provide a mature computational platform for designing IR-sensing devices based on defining the device-geometry, used materials, and operating band. As a results, nature and distribution of the generated modes are determined beside the geometry-dimensions that reflect the optimum design for sensing application. Feature like calculation of the overlapping between internal- and external-losses, known as critical coupling, can define sensing-design requirements.