Influence of non-Hermitian mode topology on refractive index sensing with plasmonic waveguides  

作　　者：Alessandro Tuniz Markus A.Schmidt Boris T.Kuhlmey 

机构地区：[1]Institute of Photonics and Optical Science(IPOS),School of Physics,The University of Sydney,NSW 2006,Australia [2]The University of Sydney Nano Institute(Sydney Nano),The University of Sydney,NSW 2006,Australia [3]Leibniz Institute of Photonic Technology(IPHT Jena),07745 Jena,Germany [4]Abbe Center of Photonics and Faculty of Physics,Friedrich-Schiller-University Jena,07743 Jena,Germany

出　　处：《Photonics Research》2022年第3期719-730,共12页光子学研究（英文版）

基　　金：Australian Research Council(DE200101041).

摘　　要：We evaluate the sensing properties of plasmonic waveguide sensors by calculating their resonant transmission spectra in different regions of the non-Hermitian eigenmode space.We elucidate the pitfalls of using modal dispersion calculations in isolation to predict plasmonic sensor performance,which we address by using a simple model accounting for eigenmode excitation and propagation.Our transmission calculations show that resonant wavelength and spectral width crucially depend on the length of the sensing region,so that no single criterion obtained from modal dispersion calculations alone can be used as a proxy for sensitivity.Furthermore,we find that the optimal detection limits occur where directional coupling is supported,where the narrowest spectra occur.Such narrow spectral features can only be measured by filtering out all higher-order modes at the output,e.g.,via a single-mode waveguide.Our calculations also confirm a characteristic square root dependence of the eigenmode splitting with respect to the permittivity perturbation at the exceptional point,which we show can be identified through the sensor beat length at resonance.This work provides a convenient framework for designing and characterizing plasmonic waveguide sensors when comparing them with experimental measurements.

关 键 词：WAVEGUIDE MODE NARROW 

分 类 号：O53[理学—等离子体物理] TP212[理学—物理]