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.

Improving the Width of Lossy Mode Resonances (LMRs) in Double-Clad Fibers

“…However, the sensitivity slightly drops with a second cladding, although for the studied experimental cases the width of the resonances is what most impacts the FOM, having better results for a fiber with second cladding. Therefore, the results obtained here for LMRs in optical fibers point in the same direction as [13] (LMRs in a Kretschmann configuration) or [14] (LPGs, improving in this case the sensitivity instead of the FWHM), suggesting that intermediate low RI layers could be a game-changer in the development of optical sensors.…”

“…On the other hand, another suggested way to improve the performance in wavelength-based sensors with thin films is to include an intermediate layer between the waveguide and the thin film, where the RI of this additional layer is lower than that of the waveguide. In [13], it is numerically studied, in a Kretschmann configuration, the addition of a lithium fluoride (LiF) intermediate layer between the optical prism and the TiO2 thin film that generates the LMR. This LiF layer reduces the FWHM of the resonances, improving the performance of the sensor.…”

Lossy Mode Resonance Sensors Based on Anisotropic Few-Layer Black Phosphorus

“…Compared to typical metal oxides, e.g., TiO 2 (n TiO 2 = 1.977 + 0.05i) and ZnO (n ZnO = 1.71749 + 0.066i), though, the imaginary part of the refractive index of BP is not relatively small: the real part is larger. From previous studies on LMR sensors based on metal oxides and BP [13,14,46], we can expect the BP structures to exhibit better sensing performance.…”

“…As the Kretschmann configuration is based on the principle of attenuated total reflection (ATR), the refractive index of the matching layer film should be lower than the refractive index of the prism. The LMR can be strongly excited when light penetrates the matching layer and is trapped by the lossy layer under a specific matching condition [13,14]. And the lossy layer serves as the LMR excitation medium.…”

Simulation of a microstructure fiber glycerol sensor based on lossy mode resonance

“…In 2015, Pathak's team proposed a SPR-based fiber sensor to measure refractive index of glycerol [13], which has reached a detection performance of -106.95 dBm/RIU. However, it is worth noting that the SPR-based sensors can only be excited by TM-polarized light, and its noble metal film layer is not only easily oxidized but also expensive, which limits its further application [14,15]. However, sensors based on another important detection principle, lossy mode resonance (LMR), overcome above shortcomings and further improve their sensitivity.…”