Liquid-Filled Hollow Core Bragg Fiber Sensors Using Different Bandgaps for High-Refractive-Index Sensing

Liang Shang,Sujuan Feng

doi:10.1109/jphot.2019.2928601

Abstract

Liquid-filled hollow core Bragg fibers (HCBFs) provide an excellent platform for refractive index (RI) sensing. The capacity for high-RI sensing based on higher order bandgaps of an HCBF is explored for higher sensitivity. We numerically compare the performances of an As2S3/PEI-based HCBF RI sensor using first-order and second-order photonic bandgaps (PBGs) for high-RI sensing. The influences of material dispersion and structural parameters on the sensing performance for both PBGs are investigated comparatively. Similar to the first-order PBG, the modification of the bandgap structure induced by material dispersion can also help to improve the linearity of an RI sensor using the second-order PBG of a conventional HCBF. For first-order and second-order PBGs including material dispersion, both a reduction in confinement loss and an improvement in sensitivity can be achieved by increasing the cladding period. In contrast, the influence of the period number on the sensitivity for a first-order PBG is contrary to that for a second-order PBG, which may be attributed to their different reflection characteristics. Furthermore, the comparative results show that a liquid-filled defect HCBF RI sensor using the second-order PBG can achieve high sensitivity and high linearity by optimizing the structural parameters of the defect layer. The proposed RI sensor would have great potential in the real-time measurement of high-RI liquid analytes.

Highlights

Refractive index (RI) sensors using microstructured optical fibers (MOFs) have attracted significant interest in the last two decades, owing to their great potential for biochemical sensing [1], [2]
The influence of the period number on the sensitivity for a first-order photonic bandgaps (PBGs) is contrary to that for a second-order PBG, which may be attributed to their different reflection characteristics
The results show that the second-order PBG is more beneficial for high sensitivity than the first-order PBG, which is essentially attributed to the difference in reflection characteristics of the multilayered cladding between them

Summary

Introduction

Refractive index (RI) sensors using microstructured optical fibers (MOFs) have attracted significant interest in the last two decades, owing to their great potential for biochemical sensing [1], [2]. The shift of the transmission spectrum with the RI of a liquid analyte filled in the air core or cladding of an MOF can be exploited as the sensing mechanism for RI measurements [3], [4]. In such an RI sensor, neither an elaborate preparation of microstructured devices [5], [6] nor an intricate coating of metal films on the surface of air holes [7], [8] is needed; the fabrication difficulty is greatly reduced.

Methods

Results

Conclusion