论文标题
分散等离激元纳米结构的拓扑优化时间域
Topology optimization of dispersive plasmonic nanostructures in the time-domain
论文作者
论文摘要
拓扑优化技术已应用于集成的光学和纳米光子学中，用于具有人类直觉无法想象的形状的设备的逆设计。在光学频率下，这些技术仅利用使用频域方法来优化非分散材料。但是，时间域的公式更有效地优化具有分散的材料。我们引入了DRUDE模型的公式，该公式被广泛用于模拟金属，导电氧化物和导电聚合物的分散性能。我们的拓扑优化算法基于有限差分时间域（FDTD）方法，我们引入了时间域灵敏度分析，该分析可以通过使用其他FDTD模拟来评估梯度信息。设计空间中介电和金属结构的存在会产生引起收敛问题的等离激元场增强。在优化迭代期间，我们采用人工阻尼方法，通过减少等离子效应，解决了收敛问题。我们介绍了2D和3D等离子体纳米antennas的几个设计示例，具有优化的现场定位和选择的频带的增强。我们的方法有可能加快宽带光学纳米结构的设计，该纳米纳米结构是用于用于纳米浮雕，集成光学，超快光子学和非线性光学的应用的分散材料制成的。
Topology optimization techniques have been applied in integrated optics and nanophotonics for the inverse design of devices with shapes that cannot be conceived by human intuition. At optical frequencies, these techniques have only been utilized to optimize nondispersive materials using frequency-domain methods. However, a time-domain formulation is more efficient to optimize materials with dispersion. We introduce such a formulation for the Drude model, which is widely used to simulate the dispersive properties of metals, conductive oxides, and conductive polymers. Our topology optimization algorithm is based on the finite-difference time-domain (FDTD) method, and we introduce a time-domain sensitivity analysis that enables the evaluation of the gradient information by using one additional FDTD simulation. The existence of dielectric and metallic structures in the design space produces plasmonic field enhancement that causes convergence issues. We employ an artificial damping approach during the optimization iterations that, by reducing the plasmonic effects, solves the convergence problem. We present several design examples of 2D and 3D plasmonic nanoantennas with optimized field localization and enhancement in frequency bands of choice. Our method has the potential to speed up the design of wideband optical nanostructures made of dispersive materials for applications in nanoplasmonics, integrated optics, ultrafast photonics, and nonlinear optics.
