Experimental demonstration of an intensity minimum at the focus of a laser beam created by spatial coherence

Application to the optical trapping of dielectric particles

Journal article (2010)
Department
Telecommunications (EEMCS) (TU Delft)
Copyright: © 2010 Optical Society of America
DOI: https://doi.org/doi:10.1364/OL.35.004166
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Published Date

13-12-2010

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Source:

Optics Letters, 35 (24), 2010

ISSN:

0146-9592

Source:

http://www.opticsinfobase.org/ol/abstract.cfm?URI=ol-35-24-4166

Faculty

Electrical Engineering, Mathematics and Computer Science

Department

Telecommunications

Abstract

In trying to manipulate the intensity distribution of a focused field, one typically uses amplitude or phase masks. Here we explore an approach, namely, varying the state of spatial coherence of the incident field. We experimentally demonstrate that the focusing of a Bessel-correlated beam produces an intensity minimum at the geometric focus rather than a maximum. By varying the spatial coherence width of the field, which can be achieved by merely changing the size of an iris, it is possible to change this minimum into a maximum in a continuous manner. This method can be used, for example, in novel optical trapping schemes, to selectively manipulate particles with either a low or high index of refraction.