Lee Jeng Yi, Chen Pai-Yen
Department of Opto-Electronic Engineering, National Dong Hwa University, Hualien 974301, Taiwan.
Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, IL 60661, USA.
Nanophotonics. 2023 May 30;12(15):3099-3108. doi: 10.1515/nanoph-2023-0157. eCollection 2023 Jul.
With consideration of parity-time (PT) symmetry, Lorentz reciprocity theorem, and real Bloch phase, we propose a generalized parametric space for any PT-symmetric unit cells that can comprehensively illustrate the PT phase transition, Bloch phase, and necessary conditions of exotic wave scattering in the general finite periodic PT photonic structures. We put forward rigorous and formal expressions of bi-directional reflectionless and coherent perfect absorption and lasing (CPAL) for the finite one-dimensional PT photonic structures. With a new concept of the parametric space, we demonstrate the necessary PT phases of general unit cells, which result in the abnormal bi-directional reflectionless and CPAL effects. Moreover, thanks to parametrization, analytical formulas for complex relative permittivities of the unit cells composed of subwavelength gain-loss heterostructure are derived to provide a guideline for manipulating different PT scattering events. We accordingly study several one-dimensional PT photonic systems to achieve exotic wave scattering enabled by PT-symmetry. We believe this work may offer a theoretical underpinning for studying extraordinary wave phenomena of PT-symmetric photonics and may open avenues for manipulation of light.
考虑到宇称时间（PT）对称性、洛伦兹互易定理和实布洛赫相位，我们为任意PT对称晶胞提出了一个广义参数空间，该空间能够全面阐释一般有限周期PT光子结构中的PT相变、布洛赫相位以及奇异波散射的必要条件。我们给出了有限一维PT光子结构的双向无反射及相干完美吸收与激光发射（CPAL）的严格且形式化的表达式。借助参数空间这一新概念，我们证明了一般晶胞的必要PT相位，这些相位会导致异常的双向无反射和CPAL效应。此外，得益于参数化，我们推导出了由亚波长增益 - 损耗异质结构组成的晶胞的复相对介电常数的解析公式，为操控不同的PT散射事件提供了指导。相应地，我们研究了几个一维PT光子系统，以实现由PT对称性实现的奇异波散射。我们相信这项工作可能为研究PT对称光子学的非凡波现象提供理论基础，并可能为光的操控开辟途径。
