Tuning the resonance of polarization-degenerate LP1,l cladding mode in excessively tilted long period fiber grating for highly sensitive refractive index sensing

Zhihong Li; Jie Shen; Qiuping Ji; Xiukai Ruan; Yaoju Zhang; Yuxing Dai; Zhennao Cai

doi:10.1364/JOSAA.35.000397

Tuning the resonance of polarization-degenerate LP_1,l cladding mode in excessively tilted long period fiber grating for highly sensitive refractive index sensing

J Opt Soc Am A Opt Image Sci Vis. 2018 Mar 1;35(3):397-405. doi: 10.1364/JOSAA.35.000397.

Authors

Zhihong Li, Jie Shen, Qiuping Ji, Xiukai Ruan, Yaoju Zhang, Yuxing Dai, Zhennao Cai

PMID: 29522041
DOI: 10.1364/JOSAA.35.000397

Abstract

This work presents a sensitive refractive index sensor based on the dual resonance of an excessively tilted long period fiber grating (Ex-TLPFG). The Ex-TLPFG is tuned to couple the guided core mode with only the polarization-degenerate cladding mode LP_1,l, which consists of TE/TM_0,l and HE_2,l vector modes. It is found that the p-polarized LP1,lp mode exhibits a higher sensitivity than that of the s-polarized LP1,ls mode. An optimized sensitivity as high as 12182.9 nm/RIU is achieved for the p-polarized LP1,2p mode at the low refractive index region by tuning the initial resonance condition. The sensing performance is also evaluated through the power measurement method for a single resonance band. It is demonstrated that the improved sensitivity in this work for diameter-reduced Ex-TLPFG is much higher than that for the conventional LPFG based devices, which makes this sensing platform very attractive for a variety of index sensing applications.