Modulation of the nonlinear optical response and transient dynamics of CdO/Ag/CdO sandwich-type films

• Published in: Optics and laser technology 2024-01, Vol.168, p.109858, Article 109858
• Main Authors: Liu, Kun, Li, Zhongguo, Li, Jie, Zhou, Wenfa, Wu, Xingzhi, Fang, Yu, Yang, Junyi, Shao, Zhangyang, Zhao, Run, Song, Yinglin
• Format: Article
• Language: English
• Subjects: C/A-time/C film; Nonlinear absorption; Nonlinear refraction; Surface plasmon resonance
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2023.109858

•The surface topography and crystallization degree of CdO/Ag/CdO films are successfully regulated by the insertion of Ag layers.•The insertion of the Ag layers enhances the electrical transport characteristics of CdO/Ag/CdO sandwich-type films.•An enhanced thermal electron transfer mechanism emerges between the CdO layer and the Ag layer.•CdO/Ag/CdO sandwich-type films have large nonlinear absorption and nonlinear refraction. Sandwich-type materials with tunable optical response and enhanced optical nonlinearity are of great importance for future nanophotonic devices. Herein, we investigate the third-order nonlinear optical response and transient dynamics of a series of CdO/Ag/CdO sandwich-type films with different Ag sputtering time. SEM images demonstrate that the Ag layer in CdO/Ag/CdO sandwich-type films change from a nanoisland to semi-continuous film with increase of Ag sputtering time. Z-scan measurements indicate that the CdO/Ag/CdO sandwich-type films exhibit huge nonlinear optical response on both femtosecond and picosecond time regime. The maximum nonlinear absorption coefficient (β = 1.605 × 10-8m/W) and nonlinear refractive index (n2 = -6.70 × 10-15m2/W) of the CdO/Ag/CdO film with 4 min Ag sputtering time are obtained in picosecond Z-scan, which are about 17 and 10 times greater than that of the single-layer CdO, respectively. Transient absorption spectroscopy results confirm the effect of increased CdO/Ag/CdO interface binding on the thermal electron transfer mechanism. A model is proposed to describe the ultrafast dynamic processes in the CdO/Ag/CdO sandwich-type films. Our results indicate the CdO/Ag/CdO sandwich-type films with tailored nonlinear optical properties are highly promising for applications of optical switches devices.