Gold nanosphere propulsion by using femtosecond laser-excited enhanced near field

Abstract

We propose nanosphere propulsion by using femtosecond laser-excited enhanced near field based on the theoretical calculations and experimental study. The optical intensity distribution and enhancement around a gold nanosphere on a silicon substrate was simulated by a 3D finite-difference time-domain method. The sphere velocities and propelled angles were calculated based on the optical intensity distribution. In our simulation, we calculated the optical intensity for the gold nanospheres with a diameter ranging from 100 to 600 nm. Calculation results show that the sphere velocity was fairly constant for the diameters ranging from 100 to 250 nm, while the velocity decreased for diameters larger than 250 nm. The propelled angle could be controlled up to only 4.6° by varying the incident angles of p-polarized waves. We have demonstrated the gold nanosphere propulsion in experiment. The gold nanospheres with a diameter of 200 nm were used in our experiments. The propelled gold particles have been melted by laser irradiation and deposited on the receiver substrate. The size and spatial distributions of gold particles have been investigated. The decrease in the laser spot size and the gap distance between the donor and receiver substrate would realize the reduction in the existence region of gold particles on the receiver substrate.