Passively Q-switched erbium-doped fiber laser using evanescent field interaction with gold-nanosphere based saturable absorber Dengfeng Fan, 1 Chengbo Mou, 2,3 Xuekun Bai, 1 Shaofei Wang, 1 Na Chen, 1 and Xianglong Zeng 1,* 1 The Key Lab of Specialty Fiber Optics and Optical Access Network, Shanghai University, 200072 Shanghai, China 2 Aston Institute of Photonic Technologies (AIPT), School of Engineering and Applied Science, Aston University, Birmingham, B4 7ET, UK 3 mouc1@aston.ac.uk * zenglong@shu.edu.cn Abstract: We demonstrate an all-fiber passively Q-switched erbium- doped fiber laser (EDFL) using a gold-nanosphere (GNS) based saturable absorber (SA) with evanescent field interaction. Using the interaction of evanescent field for fabricating SAs, long nonlinear interaction length of evanescent wave and GNSs can be achieved. The GNSs are synthesized from mixing solution of chloroauricacid (HAuCl 4 ) and sodium citrate by the heating effects of the microfiber’s evanescent field radiation. The proposed passively Q-switched EDFL could give output pulses at 1562 nm with pulse width of 1.78 μs, a repetition rate of 58.1 kHz, a pulse energy of 133 nJ and a output power of 7.7 mW when pumped by a 980 nm laser diode of 237 mW. © 2014 Optical Society of America OCIS codes: (140.3510) Lasers, fiber; (140.3540) Lasers, Q-switched; (160.4330) Nonlinear optical materials. References and links 1. F. Kong, L. Liu, C. Sanders, Y. C. Chen, and K. K. Lee, “Phase locking of nanosecond pulses in a passively Q-switched two-element fiber laser array,” Appl. Phys. Lett. 90, 151110 (2007). 2. P. P´ erez-Mill´ an, J. L. Cruz, and M. V. Andr´ es, “Active Q-switched distributed feedback erbium-doped fiber lasers,” Appl. Phys. Lett. 87, 011104 (2005). 3. J. Liu, W. Sida, Q. Yang, and P. Wang, “Stable nanosecond pulse generation from a graphene-based passively Q-switched Yb-doped fiber laser,” Opt. Lett. 36(20), 4008–4010 (2011). 4. D. Zhou, L. Wei, B. Dong, and W. Liu, “Tunable passively Q-switched erbium-doped fiber laser with carbon nanotubes as a saturable absorber,” IEEE Photon. Technol. Lett. 22(1), 9–11 (2010). 5. L. Pan, I. Utkin, and R. Fedosejevs, “Passively Q-switched ytterbium-doped double-clad fiber laser with a Cr 4+ : YAG saturable absorber,” IEEE Photon. Technol. Lett. 19(24), 1979–1981 (2007). 6. J. Xu, X. Li, Y. Wu, X. Hao, J. He, and K. Yang, “Graphene saturable absorber mirror for ultra-fast-pulse solid- state laser,” Opt. Lett. 36(10), 1948–1950 (2011). 7. B. Dong, J. Hu, C. Liaw, J. Hao, and C. Yu, “Wideband-tunable nanotube Q-switched low threshold erbium doped fiber laser,” Appl. Opt. 50(10), 1442–1445 (2011). 8. M. Amos, K. Fuse, B. Xu, and S. Yamashita, “Optical deposition of graphene and carbon nanotubes in a fiber ferrule for passive mode-locked lasing,” Opt. Express 18(22), 23054–23061 (2010). 9. H. Liu, K. Chow, S. Yamashita, and S. Set, “ Carbon-nanotube-based passively Q-switched fiber laser for high energy pulse generation,” Opt. Laser Technol. 45, 713–716 (2013). 10. H. Liao, R. Xiao, J. Fu, P. Yu, G. Wong, and P. Sheng, “Large third-order optical nonlinearity in Au: SiO 2 composite films near the percolation threshold,” Appl. Phys. Lett. 70, 1–3 (1997). #213837 - $15.00 USD Received 10 Jun 2014; revised 14 Jul 2014; accepted 15 Jul 2014; published 23 Jul 2014 (C) 2014 OSA 28 July 2014 | Vol. 22, No. 15 | DOI:10.1364/OE.22.018537 | OPTICS EXPRESS 18537