Ultrafast third-order nonlinear optical response of CdSe/Al2O3/Ag composite films

Abstract The CdSe/Al2O3/Ag composite films were deposited by magnetron sputtering and spin coating, and some samples were annealed at 450 °C. The linear absorption peak of annealed samples showed a clear redshift behavior. The femtosecond Z-scan was adopted to study the ultrafast third-order nonlinear optical response of the CdSe/Al2O3/Ag composite films. In the present study, the nonlinear properties of the composite films were 104 times higher than single CdSe quantum dots, and the properties exhibited by the unannealed samples were better than annealed samples. The increase in laser energy causes an enhancement in saturation absorption and self-focusing properties. The effects of Ag nanoparticles sputtering conditions and CdSe quantum dots content on the optical properties of the samples were also investigated. Unannealed CdSe/Al2O3/Ag composite films with Ag nanoparticles (P = 15 W) and one layer of CdSe quantum dots have the maximum value of β and χ 3 ,which are -4.80 × 10−9m/W and 3.82 × 10−9esu. Composite films can be used in optical sensing, information and communication technologies, and many other optoelectronic applications.