Nonlinear saturable absorption of nanoscaled Bi2Te3/PMMA composite film

Abstract In order to increase metallic state of surface and elevate dispersion of Bi 2 Te 3 nanoparticles, we synthesized nanoscaled Bi 2 Te 3 with a size of 91.4±2.2 nm via a hydrothermal method. Bi 2 Te 3 nanoparticles exhibit narrow distribution in size and uniform dispersion in several solvents, such as ethanol and polymethyl methacrylate (PMMA) solution. A Bi 2 Te 3 /PMMA flexible composite film was fabricated to further guarantee the uniformity of dispersion during the application. An open-aperture Z-scan technique was utilized to verify saturable absorption response of the Bi 2 Te 3 /PMMA composite film under 130 fs pulse at a wavelength of 800 nm. The nonlinear absorption coefficient β was fitted to be ~ 10 − 11 m / W , and the value of β slightly increased as the incident laser strengthened. A modulation depth of 15.1% and a saturation intensity of 18.9 GW/cm 2 for the composite film were also calculated. Our investigation suggests that the nanoscaled Bi 2 Te 3 /PMMA composite film could potentially be applied in large-energy laser pulses due to its high saturable intensity, and which might enlarge the application range of topological insulator (TI) materials.