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Abstract
We present a novel method, the optical bottle, that uses a focused laser beam to trap and analyze the optically confined multiple nanoparticles. A theoretical framework based on the mechanical equilibrium of the optical radiation pressure produced by the focused laser beam, and the osmotic pressure produced by the enriched particle concentration in the optical trap is developed for analyzing the ensemble behavior of the optically confined nanoparticles. Experiments were conducted for fluorescently labeled polystyrene nanospheres to determine the optical trapping energy of individual particles as well as the osmotic compressibility of the colloids. The new method has the advantage over conventional methods because it is not limited by the particle concentration, and is relatively easy to implement in situ.
