Figure 12.10 — Evanescent optical binding Figure 12.10 — Evanescent optical binding. (a) An example of a particle structure (hexagonal lattice) formed by 520 nm diameter polystyrene spheres in counter-propagating evanescent fields. (b) Separation of particles according to size using a combination of evanescent and propagating fields: 350 nm-diameter particles are moved to the right by a moving interference pattern between two evanescent fields, whereas 750 nm-diameter particles, which are insensitive to the spatial modulation of intensity in the standing wave, are moved to the left by unbalanced radiation pressure arising from the unequal intensities of the two beams.Figure (a) is reprinted from Mellor et al., Opt. Express 14, 10079–88. Copyright (2006) The Optical Society.Figure (b) is reprinted figure from Čižmár et al., Phys. Rev. B 74, 035105. Copyright (2006) by the American Physical Society.