“…Concurrently, new kinds of 2D materials keep emerging as new potential saturable absorbers owing to their excellent optical properties such as short recovery time, small bandgap energy, broadband absorption and high compatibility with fiber laser systems. This includes materials from the group of transition metal oxides [11][12][13], transition metal dichalcogenides [14,15] and topological insulators [16,17]. Undeniably, the advancement of these materials can be traced back to the superiority and versatility of their pioneer, graphene, which is still worthy of investigation to date [18][19][20][21][22][23][24][25].…”