Figure 5.

(A) Optical forces versus axial positions in the region below the laser focus. The solid lines show scaled predictions from the GLMT model. The experimental data show a constant-force region that is ∼330 nm deep, where the variation in force is <10%. The x axis shows the relative axial position with respect to the starting point of the measurement, which is ∼1500 nm blow the laser focus. (B) Optical potentials versus axial positions in the region below the laser focus, as obtained from an integration of the optical force shown in A along the axial direction. The linear region of the optical potential is clearly discernible.