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

In this work, poly-crystalline CaCuO 2 /CaCu 2 O 3 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 CaCuO 2 /CaCu 2 O 3 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 CaCuO 2 /CaCu 2 O 3 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 CaCuO 2 /CaCu 2 O 3 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 CaCuO 2 /CaCu 2 O 3 thin films have potential applications in nonlinear optics.