Mode-locked 2 mu m fiber laser with a multi-walled carbon nanotube as a saturable absorber

• Main Authors: Azooz, S.M., Ahmad, F., Ahmad, Harith, Harun, Sulaiman Wadi, Hamida, B.A., Khan, S., Halder, A., Paul, M.C., Pal, M., Bhadra, S.K.
• Format: Article
• Language: English
• Published: Chinese Optics Letters 2015
• Subjects: T Technology (General); TK Electrical engineering. Electronics Nuclear engineering; TL Motor vehicles. Aeronautics. Astronautics
• Online Access: http://eprints.um.edu.my/13792/1/Mode-locked_2_mu_m_fiber_laser_with_a_multi-walled.pdf; http://eprints.um.edu.my/13792/; https://www.osapublishing.org/col/abstract.cfm?uri=col-13-3-030602

We propose and demonstrate a passively mode-locked fiber laser operating at 1951.8 nm using a commercial thulium-doped fiber (TDF) laser, a homemade double-clad thulium-ytterbium co-doped fiber (TYDF) as the gain media, and a multi-walled carbon nanotube (MWCNT) based saturable absorber (SA). We prepare the MWCNT composite by mixing a homogeneous solution of MWCNTs with a diluted polyvinyl alcohol (PVA) polymer solution and then drying it at room temperature to form a film. The film is placed between two fiber connectors as a SA before it is integrated into a laser ring cavity. The cavity consists of a 2 m long TDF pumped by a 800 nm laser diode and a 15 m long homemade TYDF pumped by a 905 nm multimode laser diode. A stable mode-locking pulse with a repetition rate of 34.6 MHz and a pulse width of 10.79 ps is obtained when the 905 nm multimode pump power reaches 1.8-2.2 W, while the single-mode 800 nm pump power is fixed at 141.5 mW at all times. To the best of our knowledge, this is the first reported mode-locked fiber laser using a MWCNT-based SA.