Abstract This paper proposes and analyzes a parity-time (PT) symmetry structure based on resonant optical tunneling effect (ROTE) by using two directly coupled ROTE resonators to achieve a balanced gain-loss distribution. The unbroken/broken states of the PT symmetric system are theoretically verified by coupled-mode theory (CMT), transmission matrix method (TMM) and finite-difference time-domain (FDTD). To demonstrate the application potential, we further propose a label-free biosensing scheme that takes advantages of the square-root dependence in frequency splitting near exceptional point (EP). The theoretical results show that the sensor has a maximum sensitivity of 1 × 105 nm/IP unit (imaginary part unit of refractive index) and a theoretical detection limit of 5 × 10−10 IP unit (corresponds to 0.4 ng carcinoembryonic antigen (CEA)). Compared with the PT systems based on coupled waveguides or resonators, our design has some distinctive features. It is a multi-layer structure and does not need complicated nanoscale fabrication; the liquid samples “flow-through” the sensing region in the mid of PT structure and would greatly enhance the analyte binding efficiency as compared with the common “flow-over” manner. This simple yet highly sensitive platform would find applications in biomedical sensors, drinking water safety, and drug screening.

中文翻译：

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用于生物传感的基于共振光隧道效应的奇偶时间对称性

摘要 本文提出并分析了一种基于谐振光隧道效应（ROTE）的奇偶时间（PT）对称结构，通过使用两个直接耦合的 ROTE 谐振器来实现平衡的增益损耗分布。通过耦合模式理论（CMT）、传输矩阵方法（TMM）和有限差分时域（FDTD）理论验证了PT对称系统的未断/断态。为了证明其应用潜力，我们进一步提出了一种无标签生物传感方案，该方案利用了异常点（EP）附近频率分裂的平方根依赖性。理论结果表明，该传感器最大灵敏度为1×105 nm/IP单位（折光率的虚部单位），理论检测限为5×10−10 IP单位（对应0.4 ng癌胚抗原（CEA）） ）。与基于耦合波导或谐振器的 PT 系统相比，我们的设计具有一些独特的特点。它是多层结构，不需要复杂的纳米级制造；液体样品“流过”PT 结构中间的传感区域，与常见的“流过”方式相比，将大大提高分析物的结合效率。这个简单但高度敏感的平台将在生物医学传感器、饮用水安全和药物筛选中找到应用。液体样品“流过”PT 结构中间的传感区域，与常见的“流过”方式相比，将大大提高分析物的结合效率。这个简单但高度敏感的平台将在生物医学传感器、饮用水安全和药物筛选中找到应用。液体样品“流过”PT 结构中间的传感区域，与常见的“流过”方式相比，将大大提高分析物的结合效率。这个简单但高度敏感的平台将在生物医学传感器、饮用水安全和药物筛选中找到应用。