Domain-wall dark pulse emission in mode-locked fiber laser with Ta2AlC absorber

Abstract

In this paper, we present the first experimental generation of dark pulses in the 1550 nm band from a passively mode-locked Erbium-doped fiber laser using Tantalum Aluminum Carbide (Ta₂AlC) as the saturable absorber (SA). The Ta₂AlC SA, with a modulation depth of 6.9 %, was fabricated by integrating Ta₂AlC particles into a polyvinyl film. Dark pulse emission was observed at a pump threshold of 97.6 mW in a 151.9 m laser cavity, demonstrating that the Ta₂AlC significantly enhances the nonlinearity of the laser setup. The output spectrum reveals two peaks at 1559.6 nm and 1561.0 nm, attributed to cavity birefringence, while dark pulse formation results from cross-phase coupling between these peaks. The laser operates at a frequency of 1.25 MHz, with a pulse width of 250 ns and a maximum pulse energy of 4.76 nJ at a pumping power of 175.9 mW. Notably, the dark pulse operation exhibits promising stability, with a signal-to-noise ratio of 64 dB.