Abstract
Inspired by exceptional point (EP) sensing in non-Hermitian systems, in this work, a label-free biosensor for detecting low-concentration analytes is proposed, via a special multilayer structure: a resonant optical tunneling resonator. Due to the square root topology near the exceptional point, a recognized target analyte perturbs the system deviated from the exceptional point, leading to resolvable modes splitting in the transmission spectrum. The performance of the designed sensor is analyzed by the coupled-mode theory and transfer matrix method, separately. Here, the simulation results demonstrate that the obtained sensitivity is 17,120 nm/imaginary part unit of refractive index (IP) and the theoretical detection limit is 4.2 × 10−8 IP (regarding carcinoembryonic antigen (CEA), the minimum detection value is 1.78 ng). Instead of the typical diffusion manner, the liquid sample is loaded by convection, which can considerably improve the efficiency of sample capture and shorten the response time of the sensor. The sketched sensor may find potential application in the fields of biomedical detection, environment protection, and drinking water safety.
Highlights
As one of the top 10 discoveries in physics [24], PT symmetry is a special case of non-Hermitian systems used to study its characteristics, the operation of the sensor based on exceptional point (EP) in a PT symmetric system suffers from unstable mode detuning
We find that by adjusting the width of the coupling layer, the EP can be realized for the coupled resonant optical tunneling effect (ROTE) resonators model
The EP was realized based on the coupled ROTE resonators system in
Summary
The exceptional point (EP) was first proposed in the perturbation of linear non-Hermitian operators [1], at which the eigenvalues and the corresponding eigenstates will be degenerated [2]. Micromachines 2021, 12, 426 was proposed and designed by a parity-time (PT) coupled symmetric ROTE resonator [23]. As one of the top 10 discoveries in physics [24], PT symmetry is a special case of non-Hermitian systems used to study its characteristics, the operation of the sensor based on EPs in a PT symmetric system suffers from unstable mode detuning. General non-Hermitian systems have superiority in avoiding experimental complexity and instability [25], providing a new opportunity to explore the applications of EPs. Given the above research background, considering the complexity of balancing the gain and loss of two coupling cavities required by a PT symmetric system structure in experiments, a constructed structure with two directly coupled loss cavities was further theoretically studied. The designed biosensor has application potential in the fields of cancer diagnosis, drug screen, drinking water safety, and biomedical discoveries
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
