Optical trapping of microscopic metal particles

The optical trapping of microscopic metal particles with a fixed Nd:YAG laser beam of TEM₀₀ and TEM₀₁0 modes is demonstrated. Three kinds of metal particles (bronze, silver, and gold) used in the experiments were trapped two-dimensionally only when the laser beam focus was located near the bottom of the particle. Consideration of a simple model on the basis of ray optics indicates that a fixed single beam itself can produce a force that will pull the particle into the beam axis. A linear focal pattern also was applied to trap several particles simultaneously.