We report the first numerical analysis of the radiation force exerted on a subwavelength particle by an evanescent field localized near a subwavelength aperture. The radiation force is calculated by using the Maxwell stress tensor through the electric field distribution obtained with the finite-difference time-domain method. The result indicates that a particle moves towards the aperture. We found that if two particles exist the first particle is trapped and the second one is also attracted to the first one. The radiation force is found to be larger than the forces due to thermal fluctuations and to gravity.

• Received 24 December 1998

DOI:https://doi.org/10.1103/PhysRevLett.83.4534