Five-wavelength-switchable all-fiber erbium-doped laser based on few-mode tilted fiber Bragg grating

We demonstrate a five-wavelength-switchable erbium-doped few-mode fiber laser based on a few-mode tilted fiber Bragg grating (TFBG). The TFBG was written in a few-mode graded-index fiber and has multiple resonance characteristics. Theoretical investigations reveal that these resonances originate from mode couplings among the LP01, LP11, and LP21 modes. Switchable five-wavelength lasing with different transverse modes is obtained by careful adjustment of the polarization controller and the lateral offset between the single-mode fiber (SMF) and the few-mode fiber (FMF) located before the TFBG in the laser cavity. This wavelength-switchable laser offers the advantages of a simple structure, stable lasing and ease of operation. The proposed structure can be potentially used in applications including communications, sensing and manipulation of microscopic particles. (C) 2018 Elsevier Ltd. All rights reserved.