Trapping multiple absorbing particles in air using an optical fiber by photophoretic forces

Abstract

We demonstrate photophoretic force-based optical trapping of multiple absorbing particles in air by loosely focusing a Gaussian beam with a series of convex lenses of different focal lengths, and investigate the dependence of the number of trapped particles and their sizes on the focal length. We observe the formation of particle chains at a particular focal length, and measure the dynamic range of optical trapping for each lens system. We then develop a numerical simulation to explain the observed dynamic range of trapping by estimating the temperature distribution across a particle surface, and determining the photophoretic force. Our simulation results are in reasonable agreement with experimental results. Interestingly, we also observe that the average size of trapped particles reduces as we increase the lens focal lengths, which suggests that intensity gradients may somehow be involved in the mechanism of photophoretic trapping.

arXiv comment4 pages, 3 figs

References in corpus (5)

• Optical guiding of absorbing nanoclusters in air
• Holographic optical bottle beams
• Simultaneous measurement of mass and rotation of trapped absorbing particles in air
• Temporal dependence of optically-induced photophoretic force on absorbing airborne particles by a power-modulated laser
• Dual-mode optical fiber-based tweezers for robust trapping and manipulation of absorbing particles in air