Enhanced nonlinear optical properties of ZnS nanoparticles in 1D polymer photonic crystal cavity

The enhanced nonlinear optical absorption and optical limiting properties of polymeric one dimensional photonic crystal (1DPhC) with ZnS nanoparticles as defect are reported. The 1DPhC was fabricated by spin coating technique, using polystyrene (PS) and cellulose acetate (CA) as high and low refractive index materials. ZnS nanoparticles were synthesized in CA solution by laser ablation technique and the structural, morphological and non linear optical characterizations were done. A microcavity structure with cavity resonance around 532 nm was designed by inserting ZnS NPs/CA defect layer between two Bragg reflectors comprising 10 bilayers of CA/PS. A significant enhancement (4.6 times) in both nonlinear absorption and optical limiting properties of 1DPhC with ZnS defect layer was observed under 532 nm pulse excitation compared to the ZnS reference sample. The enhancement in the observed nonlinear optical properties of the system could be accredited to the confinement of optical field due to the localization of photons in the cavity mode. The current system can play crucial roles in designing practical nonlinear optical devices, such as optical limiters, optical switchers etc.