WSe2 thin-films as efficient optical limiters: A study on impact of annealing

Abstract We present a detailed investigation on the impact of thermal annealing on the third-order nonlinear optical (NLO) properties of sputtered WSe2 thin-films. The process of annealing results in an appreciable change in morphology and texture of WSe2 films that is governed by the annealing temperature and duration of annealing. These modifications are apparent from the electron micrographs as well as X-ray diffraction and Raman spectrum. The visible absorption spectroscopy point towards a gradual shrinkage of electronic bandgap which motivated us to explore the impact of NLO properties of the annealed WSe2 films. The NLO measurements were carried out using single-beam Z-scan technique using ultrashort pulses centered at 1030 nm excitation wavelength. The investigations reveal a distinct two-photon absorption (TPA) signature for the annealed WSe2 films along with a self-focusing effect. The observations indicate strengthening of optical limiting behaviour exhibited by WSe2 films when they are annealed for a longer duration. The outcomes suggest that the process of annealing in WSe2 films allows to control the NLO properties and renders them more suitable candidates as optical limiters for high-power applications.