“…In addition, their small size and ruggedness allowed for the development of compact Q-switched fiber lasers that could operate in rough environments. Initial work focused on graphene and carbon-based materials as SAs, including carbon nanotubes [12][13][14][15], and quickly expanded to include transition-metal oxides (TMOs) such as titanium oxide (TiO 2 ), zinc oxide Laser Physics Tunable 2.0 µm Q-switched fiber laser using a silver nanoparticle based saturable absorber (ZnO) and iron oxide (Fe 3 O 4 ) [16][17][18], as well as transitionmetal dichalcogenides (TMDs) such as molybdenum disulfide (MoS 2 ) [19], molybdenum diselenide (MoSe 2 ) [20], tungsten disulfide (WS 2 ) [21] and tungsten diselenide (WSe 2 ) [22], topological insulators such as bismuth selenide (Bi 2 Se 3 ) [23] and even more exotic materials such as black phosphorus (BP) [24,25]. In this regard, recent advances have also revealed the potential of metals such as gold (Au) and silver (Ag) for application as SAs.…”