Theoretical modeling and investigations of lossy mode resonance prism sensor based on TiO2 film

Abstract

The optical sensor based on lossy mode resonance can overcome the limitations of traditional surface plasmon resonance sensors and work under TE and TM polarized light. In this paper, an LMR sensor theoretical model with the configuration of prism/matching layer/lossy layer/sensing layer is proposed, which is based on the principle of attenuated total reflection. By using TiO2 film as the lossy layer and LiF film as the matching layer, the resonance signal under angle interrogation is effectively improved. One of the advantages of the proposed sensor is that the detection range and detection accuracy are dynamically adjustable, which provides additional degrees of freedom in the design and use of the device. The structural parameters (film thickness, layer refractive index) affecting the resonance signal have been investigated based on the electric field distribution at resonance and the coupled mode theory. The LMR signal under TE and TM polarization can be switched by changing the thickness ratio of the matching layer and the lossy layer. All possible combinations of film thicknesses are given as a reference for the design of the LMR prism sensor based on TiO2 film. Under proper thickness combination, the proposed sensor is capable of detecting the medium with refractive index ranging from 1.32 ∼ 1.47, with a sensitivity range of 34 ∼ 148 °/RIU under angle interrogation and a maximum value of 192 RIU−1 for FOM under TM polarization. We hope these investigations can prove the advantages of LMR prism sensors and provide guidance for the experimental implementation of LMR prism sensors in the future.