Tunable all-fiber all-normal-dispersion mode-locked laser of cylindrical vector beams covering the range of 69 nm.

Abstract

We propose and demonstrate an ultra-wide tunable mode-locked all-fiber laser based on nonlinear amplifying loop mirror (NALM) with the output of cylindrical vector beams (CVBs). The tuning range covers from 1029 nm to 1098 nm through the intracavity nonlinear polarization evolution (NPE) filter effect. The switchable CVBs between radially and azimuthally polarized beams with mode purity above 90% are generated by incorporating a broadband few-mode long-period fiber grating (LPFG). It is the first time to realize mode-locked CVBs near 1100 nm and the widest spectral tuning range in all-fiber laser is achieved to our knowledge. The pulsed CVBs at 1098 nm have 3 dB bandwidth of 0.31 nm with a pulse duration of 358ps.The narrow-bandwidth pulse of less than 1 nm is obtained among the whole tuning process which is of high flexibility and high tuning precision by introducing what we believe to be novel tuning mechanisms of NPE into the NALM cavity. The wide-range tunable CVBs all-fiber mode-locked laser has potential applications in high-capacity optical communication, laser imaging, and fiber optic sensing fields.