Bilal A. Ahmad, Aeriyn D. Ahmad, Muhammad Imran M.A. Khudus, Ahmad Shuhaimi A. Bakar, Masruroh, Sulaiman W. Harun
This work demonstrates the generation of Q-switched (QS) and Q-switched mode-locked (QML) pulses in an erbium-doped fiber laser (EDFL) using a Rhodamine B–based saturable absorber (SA). In a short-cavity configuration, stable QS operation centered at 1559 nm was achieved over a pump power range of 73.2–124.0 mW. The repetition rate increased to 74.5 kHz at the maximum pump power, while the highest pulse energy of 116.6 nJ was obtained at 107.1 mW. By extending the cavity with an additional 100 m single-mode fiber segment, the laser transitioned into a Q-switched mode-locked (QML) regime. Stable QML operation was established at a pump threshold of 129.7 mW following an initial unstable phase beginning at 84.5 mW. Autocorrelation measurements revealed a pulse duration of 8.25 ps, and the optical spectrum was centered at 1566.5 nm with a 3 dB bandwidth of 0.35 nm. The calculated time–bandwidth product of 0.353 indicates nearly transform-limited sech²-shaped soliton pulses. Radio-frequency analysis further confirmed stable mode-locking with clear harmonic peaks across a 200 MHz span at a fundamental frequency of 1.8 MHz. These results demonstrate that RhB–PVA is an effective SA for generating stable pulsed regimes in EDFLs. © 2026 Elsevier GmbH.
Information Institute for Postgraduate Studies, University of Information Technology and Communications, Baghdad, Iraq; Photonics Engineering Laboratory, Department of Electrical Engineering, University of Malaya, Kuala Lumpur, 50603, Malaysia; Department of Physics, University of Malaya, Kuala Lumpur, 50603, Malaysia; Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Brawijaya, Malang, 65145, Indonesia; School of Engineering and Computing, MILA University, Negeri Sembilan, Nilai, 71800, Malaysia
