Measuring the force parameters of a gradient-force optical trap for dielectric microobjects

Light-induced gradient force acting on extended dielectric microscopic objects in air is analytically calculated and measured in a direct manner. The experiments with filiform objects (cotton filament) make it possible to relate the measured gradient force to the elastic parameters of the studied material and to determine the optical parameters of the studied objects and the physical parameters of the trap. The potential application of the method for measuring optical parameters of small weight amounts of high-molecular substances and nanoobjects is analyzed.