Intense low threshold nonlinear absorption and nonlinear refraction in a new organic–polymer nanocomposite

Intense reverse saturable absorption is reported for the first time in solid films of a new organic–polymer nanocomposite, cast by doping Biebrich Scarlet dye in a vinyl polymer host polyvinyl alcohol for various concentrations, as studied employing the Z-scan technique at 442 nm under different peak incident intensities ranging from 9.37 × 102 to 104.18 × 102 W cm−2. The sample also exhibited nonlinear refraction under the experimental conditions. The estimated values of the effective coefficients of nonlinear absorption βeff(0.27 × 10−2 to 45.5 × 10−2 cm W−1) as well as nonlinear refraction n2 (−1.5 × 10−7 to −2.75 × 10−7 cm2 W−1) measured up to the highest reported ones for low power continuous wave excitation. The composite films were characterized as nanoclusters consisting of dye molecules encapsulated between larger molecules of the amorphous polymer and having a low average roughness (≈1 nm) for the surface. These results, together with the simple and flexible processing method for the dye–polymer composite, imply that BS–PVA composite films have promising optical properties as an efficient low threshold nanocomposite material for potential applications in nonlinear optical devices.

► Organic–polymer nanocomposite films of excellent surface smoothness were fabricated. ► In the Z-scan experiment, intense low threshold RSA effect observed in the dye–polymer films. ► The samples also displayed negative nonlinear refraction behaviour. ► AFM study reveals that the solid films exhibit a remarkable surface homogeneity.