Optical Levitation by Radiation Pressure

The stable levitation of small transparent glass spheres by the forces of radiation pressure has been demonstrated experimentally in air and vacuum down to pressures ∼1 Torr. A single vertically directed focused TEM00-mode cw laser beam of ∼250 mW is sufficient to support stably a ∼20-μ glass sphere. The restoring forces acting on a particle trapped in an optical potential well were probed optically by a second laser beam. At low pressures, effects arising from residual radiometric forces were seen. Possible applications are mentioned.