Tunable nonlinear optical responses in defective DNA-capped polyoxometalate ([α-SiW₁₂O₄₀]^4-) one-dimensional...

The demand for nonlinear optical materials has been rising in recent years due to their unique properties that can be suitably applied in integrated photonic devices. The technological world now focuses on low-energy-induced research outcomes globally to compete with the complexities of the higher-energy-based photonic devices. In light of this, we report the fabrication and characterization of a 1D ternary photonic crystal (PC) designed for nonlinear optical studies. The fabricated 1D ternary PC consists of silica, deoxyribonucleic acid, and zinc oxide. The defective PC is obtained by incorporating DNA-capped polyoxometalate (silicotungstate) (D-POM) thin film. The PC system has been fabricated using the dip-coating method. The linear optical properties are studied using the transfer matrix method and COMSOL software. The optical transmission properties are experimentally observed by a reflectometer. The open-aperture Z-scan experiment is conducted for observing nonlinear optical behavior. The nonlinear optical properties are studied based on the number of periods and in the presence of a defective layer as well. The results show that as the number of periods increases, the nonlinear absorption is found to decrease. Simultaneously, the system shows an increase of the saturable absorption property. The D-POM-embedded defective PC shows a drastic rise of saturable absorption. Hence, based on the nonlinear studies, the system can be applicable for tunable nonlinear optical properties. For fewer periods, the PC provided high reverse saturable absorption (RSA) at a low-threshold optical limiting value, whereas increasing the number of unit cells resulted in a saturable absorber. Hence, the 1D ternary silica/DNA/ZnO PC system, along with the D-POM-embedded defective PC system, demonstrates tunable nonlinear optical properties, making it suitable for potential photonic applications, such as optical limiting devices, saturable absorbers, ultrafast optical switching and mode-locked lasers, and nonlinear optical filters and sensors.