Figure 12.8 — Evanescent wave trapping Fig. 12.8 — Evanescent wave trapping. (a) Optical forces acting on a microparticle from unidirectional evanescent wave illumination. (b) Stable evanescent wave optical tweezers obtained by focusing an evanescent wave.Figure (a) is reprinted from Kawata and Sugiura, Opt. Lett. 17, 772–4. Copyright (1992) The Optical Society.Figure (b) is reprinted from Gu et al., Appl. Phys. Lett. 84, 4236–8. Copyright (2004) American Institute of Physics.