Towards a Precise Measurement of Surface Plasmon Optical Forces by Use of a Calibrated Evanescent Wave

摘要: Tracking the Brownian Motion of a trapped microsphere can enable precise measurement of sub-piconewton surface forces. This technique, however, is severely undermined by the nearby presence of a metal, which distorts optical fields used to trap and track the colloid. In order to make the first precise measurement of the interaction forces between a colloid and a propagating surface plasmon, we introduce a novel metallic antireflection coating and a calibration technique for absolute position particle tracking.In photonic force microscopy, an optically trapped microsphere is brought near a dielectric surface. Changes in the particle’s observed Brownian Motion yield the potential energy of the interaction between the surface and the probe. The potential energy profile, V (z), is obtained from the statistics of particle position by inverting the Boltzmann equation, such that