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

在过去几年中出现了一些高频技术，提供了有趣的功能。例如，超材料引入了具有自然界中不存在的特性的材料。它们用于构建在不同频率范围内工作的小型化天线，传感器和滤波器。 等离子体激元器件利用金属-电介质界面来引导低于衍射极限的光。这允许实现具有小得多的尺寸的光子器件，从而有望实现光子处理单元的更多集成。纳米天线（nantennas）被提出用于高频能量收集和视线通信。太赫兹（THz）的应用也出现了由于最近的太赫兹源和探测器的可用性。所有这些技术都利用其性质可能取决于源值（非线性）、取决于频率（色散）或取决于激发方向（各向异性）的材料。这些特性的不同组合可以存在于这样的高频结构中。这些复杂的特性使得这些设备的精确建模耗费大量时间和内存。 这些结构的优化通常需要估计目标响应相对于所有参数的灵敏度。 估计这些敏感性的经典方法需要重复模拟这些时间密集型结构，这可能是禁止的。

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.