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Optical trapping of nanoparticles by ultrashort laser pulses

Posted on 24. April, 2013.

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Replacing the continuous-wave- with a pulsed-mode laser in optical trapping reveals novel phenomena, including the stable trap, modifiable trapping positions, and controllable directional ejections of particles on nanometre scales. This opens unprecedented opportunities in both fundamental science and application. Hiroshi Masuhara and his colleagues discuss in Science Progress the electromagnetic formulations and physical interpretations of these new phenomena. Their aim is to show the beauty and promise of this field.

This article may not cover the full area of laser trapping, but it will give readers an overview of the growing and future challenges in this topic, particularly optical trapping with ultrashort laser pulses. It is organised as follows; we explain in brief the basic principle, experimental, and theoretical concept of optical trapping with cw lasers. We follow this by a discussion of the optical trapping of single particles or biological molecules that has been achieved by employing nanostructures. We then discuss the novel phenomena attributed to optical trapping experiments with ultrashort laser pulses. By describing nonlinear optical effects and three-dimensional optical forces exerted on dielectric particles in the trapping site that have been performed, we give particular emphasis to the electromagnetic formulations of the optical forces and physical interpretations of the new phenomena. With these interpretations, we propose a new concept of the optical trap for ultrashort laser pulses. Finally, we describe their possible future applications to challenging themes in the field of optical trapping, such as optical manipulation of biological molecules, single particle trapping, and dynamics and sorting of Rayleigh particles driven by laser pulses.

Department of Applied Chemistry, National Chiao Tung University, Taiwan
ANWAR USMAN, WEI-YI CHIANG AND HIROSHI MASUHARA

Doi: 10.3184/003685013X13592844053451

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