Wavelength-switchable noise-like square pulsed fiber laser based on nonlinear effects

Abstract

We report a fiber laser that can generate switchable wavelength noise-like square pulses (NLSPs) with a tunable pulse width based on nonlinear effects and nonlinear polarization rotation (NPR) mode-locking technology. In the single-wavelength NLSP, the 3 dB bandwidth is 1.68 nm and the central wavelength is 1558.61 nm. The widths of the spike and pulse duration are 1.47 ps and 5.14 μs. In the case of obtaining dual-wavelength noise-like squares, the pulse width is broadened from 84.4 to 875.8 ns by varying the pump power in the range of 60 to 450 mW. The dual-wavelength square pulse has a maximum energy of 27.26 nJ. The phenomena investigated in this work are conducive to a profound understanding of NLSPs formation in fiber laser and are of great significance for broadening the approach for achieving multi-wavelength square pulse.