  We demonstrate the application of Atomic Force Microscopy (AFM) based optical
force microscopy to map the optical near-fields with nanometer resolution,
limited only by the AFM probe geometry. We map the electric field distributions
of tightly focused laser beams with different polarizations and show that the
experimentally measured data agrees well with the theoretical predictions from
a dipole-dipole interaction model, thereby validating our approach. We further
validate the proposed technique by evaluating the optical electric field
scattered by a spherical nanoparticle by measuring the optical forces between
the nanoparticle and gold coated AFM probe. The technique allows for wavelength
independent, background free, thermal noise limited mechanical imaging of
optical phenomenon with sensitivity limited by AFM performance. Optical forces
due to both electric and magnetic dipole-dipole interactions can be measured
using this technique.
