Two-dimensional topological insulators/semimetals have just lately attracted a lot consideration. Nonetheless, quantum-sized topological insulators/semimetals with intrinsic traits have by no means been reported earlier than. Herein, we report the high-yield manufacturing of topological insulator (i.e., Bi2Se3 and Sb2Te3) and semimetal (i.e., TiS2) quantum sheets (QSs) with monolayer constructions and sub-4 nm lateral sizes. Each linear and nonlinear optical performances of the QSs are investigated. The QS dispersions current exceptional photoluminescence with excitation wavelength-, concentration-, and solvent-dependence. The answer-processed QSs-poly(methyl methacrylate) (PMMA) hybrid skinny movies exhibit distinctive nonlinear saturation absorption (NSA). Notably, the Bi2Se3 QSs-PMMA allows record-high NSA efficiency with broadband characteristic. Particularly, the (absolute) modulation depths as much as 71.6 and 72.4 % and saturation intensities right down to 1.52 and 0.49 MW cm-2 are achieved at 532 and 800 nm, respectively. Such phenomenal NSA efficiency would enormously facilitate their functions in mode-locked lasers and associated fields.
