Figure 2
From: Lateral optical binding between two colloidal particles
Long-rang oscillatory optical force.
(a) The magnitude and phase (inset figure) versus center-to-center separation (λ is laser wavelength in the medium ~800 nm) for the motion of the 1.5 μm-diameter polystyrene particle trapped by stationary and non-blinking traps. Here the polarization directions of the two laser beams forming the optical traps are in the YY configuration. The nonzero minima of the data in (a) decrease as 1/separation (fitted red curve), resulting from hydrodynamic interactions. By subtracting the red curve, the magnitudes of the displacements (and hence the forces) due solely to optical interactions can be determined. (b) Experimental measurements of various types of optical force on the particle in the stationary trap for 1.5 μm polystyrene particles as function of the separation. Black: total optical force with two particles in the dual beam optical trap. Red: optical interference force with a single particle in the stationary trap. Blue: optical binding force obtained by subtracting off the interference force (red dots) from the total optical force (black dots).
