Hasanain Ali, Anas Abdul Latiff, Aeriyn D. Ahmad, Masruroh, Sulaiman Wadi Harun
A polyaniline–boron nitride (PANI–BN) film was demonstrated as a saturable absorber (SA) for domain-wall dark pulse generation in a long-cavity erbium-doped fiber laser (EDFL) operating under net anomalous dispersion. Stable mode-locking was achieved over a pump power range of 129.9–212.1 mW, producing dual-wavelength emission centered at 1532.4 nm and 1557.2 nm. The dual-wavelength operation is attributed to an artificial birefringent filtering effect induced by residual polarization asymmetry from the PANI–BN film and other intracavity components. The generated dark pulses exhibited a repetition rate of approximately 1.30 MHz with a negative pulse width of 189 ns. The pulse formation is explained by domain-wall theory, where dark pulses arise from incoherent nonlinear coupling between two coexisting lasing beams oscillating simultaneously in the cavity. At the maximum pump power of 212.1 mW, the laser delivered an output power of 5.8 mW. A high signal-to-noise ratio of 70 dB at the fundamental frequency confirmed excellent pulse stability, robust mode-locking operation, and low-noise performance. These results highlight the potential of PANI–BN nanocomposites as efficient optical modulators for stable dark pulse fiber laser applications. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2026.
Fakulti Teknologi Dan Kejuruteraan Elektronik Dan Komputer (FTKEK), Universiti Teknikal Malaysia Melaka (UTeM), Hang Tuah Jaya, Durian Tunggal, Melaka, 76100, Malaysia; Photonics Engineering Laboratory, Department of Electrical Engineering, University of Malaya, Kuala Lumpur, 50603, Malaysia; Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Brawijaya, Malang, Indonesia
