Figure 12.9 — Optical waveguide forces Figure 12.9 — Optical waveguide forces. (a) Forces on a microparticle from illumination by the evanescent field of a channel waveguide. (b) Propulsion of particles along a sub-wavelength diameter tapered optical fibre.Figure (a) is reprinted from Kawata and Tani, Opt. Lett. 21, 1768–70. Copyright (1996) The Optical Society.Figure (b) is reprinted from Brambilla et al., Opt. Lett. 32, 3041–3. Copyright (2007) The Optical Society.