Wideband multi-wavelength ytterbium-doped double-clad fiber laser using Sagnac loop mirror

Abstract A wideband multi-wavelength double-cladding ytterbium-doped fiber laser (YDFL) operating in the 1080 nm region is exhibited by the use of a Sagnac loop mirror formed by the polarization maintaining fiber and assisted by the four-wave mixing (FWM) effect in a highly nonlinear fiber (HNLF). The HNLF is used in the laser cavity to produce the FWM effect in order to supply the energy of different oscillating lasing lines back into the YDF to improve the multi-wavelength operation and to increase lasing output channels. By fine-tuning the polarization controller, more than 100 lasing lines are generated within 3 dB from its peak, with a narrow wavelength spacing of 0.09 nm between the adjacent lines. With power fluctuations of just 0.67 dB the multi-wavelength exhibits wavelength drift of under 0.03 nm. To the best of the authors’ knowledge, this work presents the first realization of over 100 channels in multi-wavelength YDFLs.