We use a Gaussian laser beam to study the levitation of absorbing Mie particles. Several metal oxide particles are stably levitated, and their movement over time is recorded. Our studies show that the position of each particle is highly dependent on the other particles’ locations. The observations are explained by the phenomenon of thermal creep. The increased local pressure that is due to a temperature gradient along the particle’s surface induces levitation. The particles rest close to minima in the intensity distribution near the optical axis. An experiment is suggested that can be used to locate these minima in a laser beam.
© 2002 Optical Society of America
(120.5820) Instrumentation, measurement, and metrology : Scattering measurements
(140.7010) Lasers and laser optics : Laser trapping
(170.4520) Medical optics and biotechnology : Optical confinement and manipulation
(350.5340) Other areas of optics : Photothermal effects
Jan Huisken and Ernst H. K. Stelzer, "Optical levitation of absorbing particles with a nominally Gaussian laser beam," Opt. Lett. 27, 1223-1225 (2002)