Thermal evaporated Te-Bi2Te3 alloy thin film and its nonlinear optical properties

Te-Bi2Te3 alloy thin film has grown on silicon dioxide substrate by thermal evaporation technique. The Bi2Te3 rhombohedral structure enriched Te in the prepared thin film was identified by high solution transmission electron microscopy (HRTEM), X-Ray diffraction (XRD), Raman spectrum and X-ray photoelectron spectroscopy (XPS). Interestingly, the Te-Bi2Te3 alloy thin film presents a changeover from saturable absorption (SA) to reverse saturable absorption (RSA) as continuously increasing the input intensity, which has been investigated using the open-aperture (OA) z-scan measurement under a femtosecond-pulsed laser at 800 nm. A high modulation depth of 48.3% and large saturation intensity of 24.1GW/cm(2) of the thin film were obtained. Moreover, a large nonlinear absorption coefficient beta of similar to 10(3) cm/GW is increased with the input intensity elevated. The research results demonstrate that the Te-Bi2Te3 alloy thin film could be an emerging optical material for saturable absorber in Q-switched or mode-locking fiber lasers at low incident intensity while serve as optical limiter at high incident intensity. (C) 2017 Elsevier B.V. All rights reserved.