Optical pulling of airborne absorbing particles and smut spores over a meter-scale distance with negative photophoretic force

Abstract

We demonstrate optical pulling of single light-absorbing particles and smut spores in air over a meter-scale distance using a single collimated laser beam based on negative photophoretic force. The micron-sized particles are pulled towards the light source at a constant speed of 1-10 cm/s in the optical pulling pipeline while undergoing transverse rotation at 0.2-10 kHz. The pulled particles can be manipulated and precisely positioned on the entrance window with an accuracy of ∼20 μm, and their chemical compositions can be characterized with micro-Raman spectroscopy.