Dual dispersion turning-points-enabled highly sensitive refractive index detection using tri-core fiber helical long-period gratings.

Authors

Yunhe Zhao, Fei Pan, Zuyao Liu, Ya-Nan Zhang, Yunqi Liu, Lin Ma, Zuyuan He

Published in

Optics letters. Volume 51. Issue 18. Pages 5113-5116. Sep 15, 2026.

Abstract

This paper proposes a dual dispersion turning points (DTPs) enabled tri-core-fiber (TCF) helical long-period gratings (HLPGs) sensor, which is experimentally investigated for the first time, to the best of our knowledge. Numerical simulations and analysis show that dual DTP-related resonances can be generated within a single grating by optimizing the grating period and that the 2nd DTP-related resonance can be excited by increasing the surrounding RI. Subsequently, TCF-HLPGs samples were fabricated using a CO₂ laser and the RI sensing behaviors are experimentally investigated, confirming the realization of dual-DTPs, thereby enabling dual-region RI detection. The sensor achieves a maximum wavelength-separation sensitivity of 6653.9 nm/RIU and a transmission-contrast sensitivity of -139.1 dB/RIU, with a low temperature cross-sensitivity of 0.00017 RIU/°C. The proposed TCF-HLPGs can realize dual-DTPs-enhanced RI sensing within a single grating, providing a compact and reproducible structure for high-sensitivity and wide-range RI detection.

PMID:
42743485
Bibliographic data and abstract were imported from PubMed on 16 Sep 2026.

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