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

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 similar to 20 mu m, and their chemical compositions can be characterized with micro-Raman spectroscopy. (C) 2015 AIP Publishing LLC.