Abstract

Optical forces, or light pressure, was derived by Maxwell, and was demonstrated at the start of the 20^th century by Lebedev and by Nichols and Hull. It was studied in the 1908 Ph.D. thesis of Peter Debye on comet tails. A good review is found in Ref. [1] and in the Nobel Lecture of Bill Phillips [2]. The possibility of using such optical forces for controlling the motion and position of matter was discussed in considerable detail in very many of the early papers of Art Ashkin [3, 4], the person we honor at this symposium. In Ref. [3] he described the observation of trapped microspheres in laser light, and suggested that closely related methods could be used for confining atoms to a small region of space in a vacuum chamber. In Ref. [4] he and Jim Gordon warned that you have to think carefully about it. They proved that trapping with forces proportional to the Poynting vector couldn’t work, in analogy to the Earnshaw theorem of electrostatics, but that the trapping in [3] depended on the gradient of intensity. In many other papers he advanced the field, and is widely credited as the inventor of optical tweezers, a topic discussed by other speakers at this symposium.

© 2010 Optical Society of America