▎ 摘　　要

We demonstrate a large-energy 2-mu m double-clad Tm-doped fiber laser (DC-TDFL) Q-switched by a monopiece single-layer graphene nanosheet. The single-layer graphene is fabricated by the chemical vapor deposition (CVD) method, and then transferred onto the facet of a fiber ferrule for constructing a fiber-compatible saturable absorber (SA). The Q-switching operation of the DC-TDFL at 1980 nm is achieved and has a large pulse energy of 1.06 mu J (corresponding to the average output power of 28.6 mW). The narrowest pulse duration is 2.7 mu s, and the pulse repetition rate can be tuned from 8 to 27 kHz by changing the pump power from 2.35 to 2.82 W. To the best of our knowledge, this work is not only the first demonstration of a 2-mu m Q-switched all-fiber laser using monopiece single-layer CVD graphene as a SA, but also generates the largest pulse energy from graphene-based all-fiber DC-TDFLs. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)