Fabrication and Characterization of Line-by-Line Inscribed Tilted Fiber Bragg Gratings Using Femtosecond Laser

Hongye Li; Xiaofan Zhao; Binyu Rao; Meng Wang; Baiyi Wu; Zefeng Wang

doi:10.3390/s21186237

Fabrication and Characterization of Line-by-Line Inscribed Tilted Fiber Bragg Gratings Using Femtosecond Laser

Sensors (Basel). 2021 Sep 17;21(18):6237. doi: 10.3390/s21186237.

Authors

Hongye Li^{1

2}, Xiaofan Zhao^{1

3}, Binyu Rao^{1

3}, Meng Wang^{1

2

3}, Baiyi Wu^{1

2

3}, Zefeng Wang^{1

2

3}

Affiliations

¹ College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China.
² State Key Laboratory of Pulsed Power Laser Technology, Changsha 410073, China.
³ Hunan Provincial Key Laboratory of High Energy Laser Technology, Changsha 410073, China.

Abstract

In this paper, we studied the basic characteristics of tilted fiber Bragg gratings (TFBGs), inscribed line-by-line. Experimental results showed that if the TFBGs were located within different planes parallel to the fiber axis, the spectra performed differently. For 2°TFBG, if it was located near the central plane, the Bragg resonance was stronger than ghost mode resonance, and the order reversed if it was located near the boundary between core and cladding. As the tilted angle increased, the range of cladding mode resonance increased. When the tilted angle was larger than 12°, the birefringence effect was observed. Based on the birefringence phenomenon, torsion characteristics were experimentally studied; the sensitivity was about 0.025 dB/degree in the linear variation range. The harmonic order of TFBGs also affected the transmission spectrum. Leaky mode resonance was observed in the 8th order TFBG, and torsion (or polarization) influenced the spectrum of the 8th order TFBG. Our research represented the theory of line-by-line inscribed TFBGs and provided an inscription guidance for TFBGs.

Keywords: direct writing; femtosecond laser; tilted fiber Bragg gratings.

Abstract

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