Optical guiding of particles is traditionally associated with forces of radiation pressure, and a vast majority of optical traps are based on the ponderomotive forces. However, the developed analysis suggests an additional possibility of trapping which stems from thermal interaction of the laser-irradiated particle and environment via photophoretic forces. Photophoretic forces are based on a transfer of energy from a particle absorbing light to molecules of an ambient gas. As was demonstrated recently [1], the photophoretic force provides a major approach to the stable trapping of absorbing particles in gas media in a trap created by two counter-propagating optical vortices. For example, the photophoretic forces in air at normal conditions are several orders of magnitude stronger than the radiation pressure for a 1-micron size particle. Therefore, the translation distance, acceleration, as well as the translated mass of particles in such optical duct can reach unprecedented values.
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