Digest Journal of Nanomaterials and Biostructures Vol. 14, No. 1, January - March 2019, p. 23 - 27 PASSIVE Q-SWITCHING OPERATION OF ERBIUM-DOPED FIBER LASER WITH GOLD NANOPARTICLES EMBEDDED INTO PVA FILM AS SATURABLE ABSORBER A. R. MUHAMMAD a , A. H. A. ROSOL a , R. A. A. TAHRIN b , N. S. AZMAN b , S. KASSIM b , M. A. ISMAIL a , Z. JUSOH c , S. W. HARUN a,d,* a Photonics Engineering Laboratory, Department of Electrical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia. b Advanced Nanomaterial Group, School of Fundamental Science, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia c Faculty of Electrical Engineering, UniversitiTeknologi MARA(Terengganu), 23000 Dungun, Terengganu, Malaysia d Department of Physics, Faculty of Science and Technology, Airlangga University, Surabaya 60115, Indonesia 50603, Malaysia We demonstrate a Q-switched Erbium-doped fiber laser (EDFL) using a newly developed gold nanoparticles (GNPs) based saturable absorber (SA) for the first time. The GNPs were embedded in polyvinyl alcohol (PVA) for film-forming and inserted into an Erbium-doped fiber laser (EDFL) cavity to achieve passive Q-switching. The Q-switched EDFL operates at 1560 nm with a pump power threshold of 35 mW, a pulse repetition rate tunable from 19.7 to 89.9 kHz, and the smallest pulse-width of 2.64 μs. The Q-switching pulse shows no spectral modulation with a peak-to-pedestal ratio of 69 dB indicating the high stability of the laser. The highest pulse energy of 103 nJ was obtained at 118 mW pump power. These results show that the GNPs based SA is available for pulsed operation in the 1550 nm spectral range. (Received May 23, 2018; Accepted January 9, 2019) Keywords: Q-switching,Rose goldnanoparticle,Passive saturable absorber,EDFL 1. Introduction Q-switched fiber lasers are widely employed in applications which require high pulse energy such as range finding, remote sensing, optical communication, laser processing, and etc. [1, 2]. They are typically obtained based on the modulation of the quality factor, Q of a cavity, which can be realized by either active or passive technique. Compared with the active technique, passive Q-switching based on intensity saturable absorbers (SAs) possesses the advantages of compactness, low cost, and simple cavity configuration. It has been reported that various kinds of functional materials are used as SAs to achieve passive Q-switching, such as graphene [3], gold nanorods[4], carbon nanotubes [5], Bi 2 Se 3 [6], MoS 2 [7], WS 2 [8], and so on. However, there are still interest on exploring other new SA materials and designing new schemes for realizing passive Q- switched EDFLs. Despite many methods and new materials are explored in developing the SA for Q- switching pulse generation, metal nanoparticles-based SA especially transition metal elements are rarely being investigated. These elements pick up a great interest amongst scientific researchers as they hold a unique optical property such as ultrafast response time, broad saturable absorption band and large third-order nonlinearity [6]. Very recently, Wu et. al. reported a Q-switching pulse generation by using Copper Nanowires (CuNW) as saturable absorber at visible range laser region (635 nm) with repetition rate ranging from 239.8 – 312.4 kHz, pulse width of 0.685 - 0.394 μs and * Corresponding author: swharun@um.edu.my