Template-free fabrication of Ag nanowire arrays/Al2O3 assembly with flexible collective longitudinal-mode resonance and ultrafast nonlinear optical response

摘要: We utilized a co-sputtering technique without any templates, featuring growing and etching synchronously, to delicately fabricate dense and ultra ne Ag nanowire arrays/alumina matrix composite lms. Both the diameter and separation distance of the Ag nanowire arrays in the composites are not only within the scope of sub-10 nm but also tunable, which is very hard to accomplish for the conventional optical lithography- or template-based method. It is exhibited that the collective longitudinal plasmon resonance of the composite lms, covering a wide range from visible to the near infrared region, is extremely sensitive to the geometrical parameters of the Ag nanowires, owing to the strong plasmonic coupling among neighboring nanowires. The experimental observations were also theoretically supported by the near- eld electromagnetic numerical simulation. More interestingly, the fabricated composite lms demonstrated ultrafast nonlinear optical response in the visible light region under femtosecond laser excitation, possessing a short relaxation time of 1.45 ps for the longitudinal mode (L mode) resonance. These results indicate that the proposed composite lms as a building block with exotic optical properties could provide an opportunity to construct integrated nanodevices for plasmonic optical applications.