The 2018 Nobel Prize in Physics was awarded (50%) to Arthur Ashkin “for the optical tweezers and their application to biological systems”. Optical tweezers rely on the ponderomotive force: a dielectric is attracted to a region of high mean squared electric field. Thus the focus of a laser beam can trap a dielectric. A tiny dielectric bead attached to a biological system (e.g., cell or DNA) allows the system to be manipulated (e.g., moved, stretched, set into oscillations) and studied.

Behind the applications is the theory of the ponderomotive force, wherein several subtleties have been elucidated by our group at CUHK, starting with a work in 1976 (Lai and Young, Phys. Rev. A 14, 2329) on radiation pressure “in satisfactory agreement with the recent experimental result of Ashkin and Dziedzic”.

The application of optical tweezers and the interesting issues relating to the ponderomotive force will be described.

Photos: Please click HERE.