Broadband Fe3O4 nanoparticles saturable absorber for Q-switched fiber lasers

Abstract We demonstrated passively Q-switched 1-, 1.5-, and 2-μm fiber lasers by exploiting ferroferric-oxide nanoparticles (FONPs) as a broadband saturable absorber (SA). FONPs were prepared by a method of thermal decomposition, and then were mixed with sodium carboxymethylcelluose (NaCMC) to form a FONPs film. The FONPs film was sandwiched between two fiber ferrules to fabricate the FONPs SA, which had a broadband absorption from 800 to 2000 nm and nonlinear saturable absorption at 1-, 1.5-, and 2-μm. By inserting the same FONPs SA into the ytterbium, erbium and thulium doped fiber laser cavities, the stable passively Q-switching operation at 1039, 1560 and 1982 nm was realized for a threshold pump power of ∼82 mW, ∼62 mW and ∼830 mW, respectively. To the best of our knowledge, it is the first demonstration of the use of a single SA based on FONPs for wide-band Q-switching operation of fiber lasers from 1 to 2 μm.