Nonlinear optical properties of ZnS nanocrystals incorporated within the polyvinyl alcohole photopolymer matrices

Abstract

AbstractPhotoinduced nonlinear optical effects in ZnS nanocrystallites incorporated within the photopolymer polyvinyl alcohol matrices were studied. As a basic method we have used photoinduced optical second harmonic generation (SHG). The Q‐switched HF‐laser (λ = 2.64.μm; pulse duration 30‐40 ps) was used as a source of probing (fundamental) light beam and the pulsed nitrogen (λ = 337.7 nm) was applied as a source of the photoinducing pump light. With increasing photoinducing beam power, the output SHG signal (at λ = 1.32 μm) increases. The maximal second‐order non‐linear optical susceptibility corresponds to tensor component d123 = d14 = 3.8 ± 0.2 pm/V at a photoinducing power density equal to about 1.25 GW/cm2. With decreasing temperature, the SHG signal increases within the temperature range 25‐30 K. Time‐dependent pump‐probe measurements of the SHG indicate an existence of the SHG maximum for a pump‐probe delaying time 20 ps. The ZnS hexagonal structural components play a crucial role in the observed photoinduced second‐order non‐linear optical effects. Large values of the non‐linear optical constants as well the good technological parameters open a possibility to enhance the non‐linear optical susceptibilities of the investigated ZnS nanocrystallites.