Nonlinear optical absorption of thin films containing Ag <sub>9</sub> GaS <sub>6</sub> , AgInS <sub>2</sub> , and CuGaS <sub>2</sub> nanocrystals
Abstract
Abstract A series of sulfide nanocrystals was prepared using a new reagent. The properties of the nanocrystals and of thin films containing them were investigated using spectroscopic, morphological and nonlinear optical methods. The two-photon absorption, three-photon absorption, and saturable absorption of the thin (30–80 nm) films containing different number of layers of the nanocrystals of three sulfides (Ag 9 GaS 6 , AgInS 2 , and CuGaS 2 ) were studied using the 1030 nm and 515 nm, 200 fs probe pulses. The prevailing role of either saturable absorption or three-photon absorption was demonstrated in the case of Ag 9 GaS 6 and CuGaS 2 films by varying the intensity of the 1030 nm probe pulses. In the case of 515 nm probe pulses, the two-photon absorption in AgInS 2 film was observed at small intensities followed by saturable absorption at higher intensities of the probe pulses. The three-photon absorption coefficients of Ag 9 GaS 6 and CuGaS 2 films were measured to be 2.2 × 10 –21 cm 3 W− 2 and 6 × 10 –19 cm 3 W −2 , while two-photon absorption coefficient of AgInS 2 film was determined to be 3.6 × 10 11 cm 1 W −1 .