Spectral and Sensing Performance of Long-Period Fiber Gratings at 2 μm Waveband
Yunhe Zhao, Wei Wang, Yunqi Liu, Zuyao Liu, Xuping Zhang, Yongsheng Yang
Abstract
In this paper, we demonstrate the transmission spectral and surrounding refractive index (SRI) sensing performance of long-period fiber gratings (LPFGs) at 2 μm waveband. The cladding modes operating at 2 μm waveband show higher SRI sensitivity than 1.55 μm waveband. The influence of a little off resonance region of grating period, refractive index modulation and duty cycle of gratings are analyzed theoretically. Additionally, the LPFGs of LP<sub>08</sub> mode near dispersion turning point operating at 2 μm waveband are investigated theoretically and experimentally. Mode splitting brings out with the increasing SRI. After the resonant dip splitting into two dips (dip A and dip A′), the SRI sensitivity of dip A are measured to be as high as −8495.2 nm/RIU in the SRI region of 1.445–1.457. The proposed 2-μm-waveband LPFGs makes it a potential in biochemical and environmental monitoring.