Proceedings of the National Academy of Sciences of the United States of America

About the PNAS Member Editor
Name Ashkin, Arthur
Location Bell Labs
Primary Field Physics
Secondary Field Engineering Sciences
 Election Citation
Ashkin is known for his pioneering experimental and theoretical work on the manipulation of particles with light, including the invention of the "optical tweezers" laser trap and his studies of radiation forces on atoms, and for his contributions to photorefraction, second harmonic generation, and non-linear optics in fibers.
 Research Interests
As a physicist, I have been interested in microwaves and laser light. With microwaves, I studied parametric amplification of space charge waves and low noise cyclotron waves. With lasers I and my group initiated use of cw beams for study of nonlinear optical processes. We discovered the photorefractive effect and started study of nonlinear effects in silica optical fibers. In 1969 I initiated study of optical manipulation of small transparent neutral particles and atoms using radiation pressure forces. These forces are sufficient to accelerate, decelerate, deflect, guide, levitate, and stably trap particles. The simplest trap, the so-called "optical tweezers trap," consists of a single, strongly focused beam. Optical traps offer unique advantages for studying individual particles. Particles in the size range from 100's of angstroms to 10's of microns were trapped and studied. Surprisingly, we found tweezers can also manipulate single living cells, bacteria, viruses, and even organelles within cells. This work initiated use of optical manipulation for biology. With atoms, we demonstrated focusing and guiding of atomic beams by light, the first cooling of atoms by "optical molasses," and optical trapping of cooled atomic vapors. Use of optical manipulation by physical scientists, and biologists is growing rapidly. Recent advances in physics and biology using optical manipulation include achievement of Bose-Einstein-Condensation in atomic vapors at submillikelvin temperatures, demonstration of atom lasers, and detailed measurements on individual motor molecules.

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