Modeling and Design Optimization of High Frequency Micro and Nano Structures Exploiting Adjoint Sensitivity Analysis

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A number of high frequency technologies emerged over the past few years that offer interesting functionalities. Metamaterials, for example, introduced materials with properties that do not exist in nature. They are used in building miniaturized antennas, sensors, and filters that operate in different frequency ranges. Plasmonic devices utilize metal-dielectric interfaces to guide light below the diffraction limit. This allows the implementation of photonic devices with much smaller dimensions thus promising more integration of photonic processing units. Nano antennas (nantennas) were presented for high frequency energy harvesting and line-of-sight communication. Terahertz (THz) applications also emerged thanks to the recent availability of THz sources and detectors. All these technologies utilize materials whose properties may be dependent on source values (nonlinear), dependent on frequency (dispersive), or dependent on the direction of excitation (anisotropic). Different combinations of these properties may exist in such high frequency structures. These complex properties make the accurate modeling of these devices time- and memory-intensive. Optimization of these structures often requires estimating sensitivities of the target response with respect to all parameters. The classical approach for estimating these sensitivities requires repeated simulations of these time-intensive structures which may be prohibitive.***In this proposal, we will build on our expertise in adjoint sensitivity analysis to develop universal adjoint sensitivity approaches. These approaches will apply to general high frequency structures whose materials may exhibit any combination of nonlinearity, dispersion, and anisotropy. Using our approaches, the sensitivities of the desired response or objective function will be estimated using at most one extra simulation regardless of the number of parameters. Adjoint sensitivities will be applied to the design optimization of metamaterial structures, plasmonic structures, nantennas, and THz filters and frequency selective surfaces. We will apply our developed adjoint techniques to the area of wideband cloaking where a cloak can possess a large number of optimizable parameters. We will also utilize adjoint sensitivity analysis to improve the accuracy of THz imaging and spectroscopy of different samples.***The proposed research addresses important areas of research for Canada and the world including energy harvesting, THz medical imaging, and wideband cloaking of electrically large objects. It will result in novel technologies that will be utilized by Canadian companies to create new products or develop existing ones. It will also train a good number of high quality personnel (HQP) on modeling, design optimization, fabrication, and characterization of advanced high frequency micro and nano structures. **