Harith Ahmad, N. Mokhtar, N.A.M. Rusni, M.S.M. Sa’ad, I.S. Imaduddin, S.R. Majid, M.Z.H. Mayzan, M.A.M. Lutfi, Mousa Hussein, S. Sun, K. Thambiratnam
Ultrafast fiber lasers operating in the 2 μm spectral region require robust and highly nonlinear saturable absorbers (SAs) to achieve stable mode-locking. This study demonstrates that a calcium-molybdenum-cobalt-2-methylimidazole (CaMoCo-MIM), a trimetallic organic framework (TMOF), functions as an efficient SA, enabling stable and self-starting mode-locking pulse in a thulium–holmium-doped fiber laser (THDFL). The CaMoCo-MIM exhibits excellent nonlinear optical performance, achieving a high modulation depth of 36.2%, surpassing many previously reported MOF-based SAs, as supported by the comparative data presented in this study. Stable soliton pulse generation was realized at a pump power of 307 mW, producing a central wavelength of 1895.21 nm, a 3 dB spectral bandwidth of 3.03 nm, and a pulse duration of 1.25 ps. A time-bandwidth product (TBP) of 0.316 indicates a nearly chirp-free pulse. Long-term operation over four hours confirmed robust stability with a constant repetition rate of 14.6 MHz. This TMOF establishes a high-modulation-depth SA in next-generation lasers. © The Author(s) 2026.
Photonics Research Centre, Universiti Malaya, Kuala Lumpur, 50603, Malaysia; Institute for Advanced Studies, Universiti Malaya, Kuala Lumpur, 50603, Malaysia; Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Negeri Malang, Jalan Semarang 5, Malang, 65145, Indonesia; Centre for Ionics, Department of Physics, Universiti Malaya, Universiti Malaya, Kuala Lumpur, 50603, Malaysia; Department of Physics and Chemistry, Faculty of Applied Sciences and Technology, Universiti Tun Hussein Onn Malaysia, Pagoh Higher Education Hub, Johor, Panchor, 84600, Malaysia; Department of Electrical and Communication Engineering, United Arab Emirates University, Al Ain, United Arab Emirates; School and Mechanical and Automotive Engineering, Qingdao University of Technology (QUT), Qingdao, China; Physics Department, Kulliyyah of Science, International Islamic University Malaysia, Bandar Indera Makhota, Kuantan, Pahang, 25200, Malaysia
