Yan Wei, Lalanne Philippe, Qiu Min
Key Laboratory of 3D Micro/Nano Fabrication and Characterization of Zhejiang Province, School of Engineering, Westlake University, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province, China.
Institute of Advanced Technology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province, China.
Phys Rev Lett. 2020 Jul 3;125(1):013901. doi: 10.1103/PhysRevLett.125.013901.
When material parameters are fixed, optical responses of nanoresonators are dictated by their shapes and dimensions. Therefore, both designing nanoresonators and understanding their underlying physics would benefit from a theory that predicts the evolutions of resonance modes of open systems-the so-called quasinormal modes (QNMs)-as the nanoresonator shape changes. QNM perturbation theories (PTs) are one ideal choice. However, existing theories developed for tiny material changes are unable to provide accurate perturbation corrections for shape deformations. By introducing a novel extrapolation technique, we develop a rigorous QNM PT that faithfully represents the electromagnetic fields in perturbed domain. Numerical tests performed on the eigenfrequencies, eigenmodes, and optical responses of deformed nanoresonators evidence the predictive force of the present PT, even for large deformations. This opens new avenues for inverse design, as we exemplify by designing super-cavity modes and exceptional points with remarkable ease and physical insight.
当材料参数固定时，纳米谐振器的光学响应由其形状和尺寸决定。因此，设计纳米谐振器并理解其 underlying 物理过程都将受益于一种理论，该理论可预测开放系统（即所谓的准正常模式 (QNM)）的共振模式随纳米谐振器形状变化的演变。QNM 微扰理论 (PT) 是一个理想选择。然而，现有的针对微小材料变化而开发的理论无法为形状变形提供准确的微扰校正。通过引入一种新颖的外推技术，我们开发了一种严格的 QNM PT，它能忠实地表示受扰域中的电磁场。对变形纳米谐振器的本征频率、本征模式和光学响应进行的数值测试证明了当前 PT 的预测能力，即使对于大变形也是如此。这为逆向设计开辟了新途径，我们通过轻松且富有物理洞察力地设计超腔模式和奇异点来举例说明。
