AFM observation of force on a dielectric sphere in the evanescent field of totally reflected light
Jožef Stefan Institute - Jamova 39, Ljubljana, Slovenia
2 Department of Physics, University of Ljubljana - Jadranska 19, Ljubljana, Slovenia
Accepted: 15 May 1998
We present the first direct measurement of the radiation pressure force acting on a sphere in the evanescent field of a totally reflected light beam using the atomic force microscope (AFM). A dielectric sphere was attached to the AFM cantilever and placed into the evanescent light field of the Ar-laser beam illuminating a sapphire prism surface at an angle larger than the critical. A repulsive force due to the evanescent field was observed. The force decreases exponentially with the characteristic length of nm as the distance between the sphere and the total reflection surface increases. The measured magnitude of the force close to the surface is N. Both the magnitude and the decay length are in good agreement with the calculated values.
PACS: 61.16.Ch – Scanning probe microscopy: scanning tunneling, atomic force, scanning optical, magnetic force, etc / 42.25.Bs – Wave propagation, transmission and absorption / 42.25.Gy – Edge and boundary effects; reflection and refraction
© EDP Sciences, 1998