posted on 2024-07-09, 18:57authored bySmitha Kuriakose, Dru Morrish, Xiaosong Gan, James ChonJames Chon, Kishan Dholakia, Min Gu
We report the focused evanescent optical trapping of nonfluorescent and fluorescent dielectric microspheres using a femtosecond laser. The experiment confirms that the trapping efficiency increases with the size of the particles. As a result, a pulsed laser has been used to trap particles in the Mie regime and to excite whispering gallery modes in them. The excitation of whispering gallery modes in a near-field femtosecond trap shows a significant suppression of the two-photon fluorescence background with an improvement of the photon storage factor by 46%, as compared to far-field two-photon excitation.