Domain-wall dark pulse generation with polyacrylonitrile as saturable absorber

We have demonstrated a domain-wall dark pulse by using a polyacrylonitrile film as a saturable absorber (SA) in Erbium-doped fiber laser (EDFL) cavity. The preparation of the polyacrylonitrile thin film SA and the performance analysis of the film were described. The dual wavelengths are stably lased at 1560.43 nm and 1561.17 nm to induce topological defect in temporal domain. Within the pumping range of 97.76–165.26 mW, we observed the dark pulse oscillation in the fiber laser cavity with repetition rate of 0.99 MHz and pulse width of 306 µs. The highest average pulse energy of 6.54 nJ was achieved at pump power of 165.26 mW, with a signal-to-noise ratio of 67 dB. The stable formation of dark pulses in the fiber laser system demonstrates that the polyacrylonitrile thin film SA has significant potential for commercial applications. This advancement not only highlights its promise for future industry use but also establishes a foundation for growth in sustainable technologies.