N.A.M. Rusni, H. Ahmad, I.S. Imaduddin, Mousa Hussein
This study presents the development of a novel bismuth nanoparticle/nitrogen-doped carbon (BiNP/NC) nanocomposite, successfully integrated onto an arc-shaped fiber to serve as an advanced saturable absorber (SA) for ultrafast photonics. Compositional and microstructural evaluations verified the successful integration of BiNPs into the N-doped carbon matrix, yielding a high modulation depth of 33.3 %. When integrated into a dual-pump thulium-holmium-doped fiber laser (THDFL) cavity, the BiNP/NC SA enabled self-starting, fundamental-harmonic mode-locked pulses centred at 1897 nm. The generated pulse exhibited a fundamental frequency of 14.5 MHz, a pulse duration of 1.22 ps, and a signal-to-noise ratio (SNR) of 52.4 dB. The fundamental-harmonic mode-locked pulses remained stable over a two-day continuous observation, with both the optical and RF spectra remaining stable for four hours of uninterrupted operation each day. By increasing the pump power, higher harmonic orders of mode-locked pulses were achieved, reaching up to the 12th harmonics. These results demonstrate the BiNP/NC nanocomposite as a promising SA for high-repetition-rate ultrafast photonics in the ∼ 2 µm wavelength region. © 2026
Photonics Research Centre, Universiti Malaya, Kuala Lumpur, 50603, Malaysia; Institute for Advanced Studies, Universiti Malaya, Kuala Lumpur, 50603, Malaysia; Physics Department, Faculty of Science, Universiti Malaya, Kuala Lumpur, 50603, Malaysia; Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Negeri Malang, Jalan Semarang 5, Malang, 65145, Indonesia; Distinguished Visiting Professor, Universiti Kuala Lumpur British Malaysian Institute, (UniKL BMI), Batu 8, Jalan Sungai Pusu, Selangor, 53100, Malaysia; Centre for Ionics, Universiti Malaya, Department of Physics, Kuala Lumpur, 50603, Malaysia; Department of Electrical and Communication Engineering, United Arab Emirates University, Al Ain, United Arab Emirates
