Low-threshold saturable absorption and photoluminescence emission in Phenol Red dye impregnated poly(vinyl alcohol) nanocomposite

A new organic-polymer nanocomposite system constituted of organic chromophore Phenol Red (PR) was fabricated using poly(vinyl alcohol) (PVA) as host template. The structure, morphology, linear and nonlinear optical absorption as well as photoluminescence emission behaviour of the organic-polymer composites were investigated. The composite films were characterized as nanoclusters consisting of the dye molecules encapsulated between the larger molecules/molecular chains of the semicrystalline polymer and having an average roughness as low as ≈0.62 nm for the surface. XRD studies indicated an increase in the semicrystalline nature of PVA, with the addition of Phenol Red (PR) dye molecules into the polymer. The composite films exhibited PL emission in the orange-red region of the visible spectrum, when excited in the vicinity of its absorption maximum. An investigation into the absorptive nonlinearity exhibited by the Phenol Red-PVA nanocomposite system under low power continuous wave (cw) laser light illumination at 442 nm, performed using the Z-scan technique is presented. The samples exhibited saturable absorption under the experimental conditions. The estimated values of the saturation intensity were found to be very low. The results indicate that the nanocomposite films can be potential candidates for applications in light emitting devices and also as low threshold saturable absorbers.