Theoretical Analysis of a Novel Microstructure Fiber Sensor Based on Lossy Mode Resonance

Xue-Zhou Wang,Qi Wang

doi:10.3390/electronics8050484

Abstract

In this paper, we proposed a novel D-shaped microstructure fiber sensor based on lossy mode resonance (LMR). TiO2/HfO2 bilayer film is coated on the exposed-core portion of photonic crystal fiber (PCF) as a sensing channel. The asymmetrical LMR region generates strong birefringence, which leads to the separation of X polarization and Y polarization. This structure excites a stronger evanescent field than the conventional D-shaped fiber, thereby greatly improving the sensor sensitivity. Additionally, the metallic oxide bilayer can further enhance the sensor’s performance. We numerically investigated the influence of the number of air holes removed in PCF on the sensor performance and the proportion of TiO2 to HfO2 in theory for the first time. The results show that an ultra-high sensitivity of 140,000 nm/RIU is obtained, which is an order of magnitude higher than that of surface plasmon resonance sensors with a similar waveguide structure and LMR sensor coated film. This achievement means that LMR-based sensing systems are more sensitive than many sensors in real-time and distributed measurements, which will play an extremely important guiding role in the structural design of microstructure fiber sensors in the future.

Highlights

The optical waveguides based on nanofilm coatings have been widely investigated over the past decades [1]
The second phenomenon is known as lossy mode resonance (LMR), which is generated by lossy dielectrics with positive permittivity and a higher refractive index than both waveguides and surrounding medias
Plating TiO2 /HfO2 film can be prepared by both magnetron sputtering deposition and chemical vapor deposition, which is much easier to implement than coating a film on the air hole wall of photonic crystal fiber (PCF)

Summary

Introduction

The optical waveguides based on nanofilm coatings have been widely investigated over the past decades [1]. The third is called long-range surface exciton polariton (LRSEP), which is generated by the dielectrics, whose permittivity is with near-zero real part and large imaginary part [6] This case is beyond the category of this research and will not be mentioned further. The flexibility of the utilization of film materials and numerous fabrication techniques, unlike SPR based devices, is another important advantage of the fabrication of LMR optical fiber sensors. Luan et al have simulated an SPR sensor based on D-shaped all-solid hollow core photonic crystal fiber whose sensitivity can reach 2900 nm/RIU. We propose a novel D-shaped microstructure fiber sensor based on LMR This structure excites a strong evanescent field, thereby greatly improving the sensitivity of the sensor. This paper plays a significant role in the structural design of microstructure fiber sensors

Sensor Structure and Theoretical Modelling

Results and Discussion

Electric

Loss of spectra of x-polarized and y-polarized peaks at analyte

Conclusions