Fabrication and characterization of CaCuO2/CaCu2O3 thin films with enhanced third-order nonlinear properties

In this work, poly-crystalline CaCuO2/CaCu2O3 thin films were deposited on quartz substrates using radio frequency (RF) magnetron sputtering and subsequent annealing. The deposition process was performed at room temperature under an oxygen partial pressure of 4 × 10−2 Pa at a speed of 2 Å/s. The crystalline structure, distribution of the particles and size of the elements of the as-prepared and CaCuO2/CaCu2O3 thin films were individually acquired and discussed in detail. Subsequent annealing was found to modify the composition, structure and morphological characteristics of the as-prepared thin film, resulting in changes of the film quality and, thereby, improving the nonlinear optical (NLO) response of the film. The sign and magnitude of third-order nonlinear susceptibility χ(3) of the as-prepared and CaCuO2/CaCu2O3 thin films were determined using the top-hat Z-scan technique performed at 532 nm with a laser duration of 190 fs. The results show that annealed CaCuO2/CaCu2O3 thin film exhibits a fast NLO response with a third-order nonlinear susceptibility χ(3) of 1.1 × 10−12 esu, which is higher than that of the as-prepared thin film. The results indicate that CaCuO2/CaCu2O3 thin films have potential applications in nonlinear optics.