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Proceedings Paper

Beam tapering effect in microsphere chains: from geometrical to physical optics
Author(s): Kenneth W. Allen; Arash Darafsheh; Vasily N. Astratov
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Paper Abstract

By using polystyrene microspheres with index n=1.59 as a model system we study light focusing and transport properties of chains formed by spheres with diameters varying from 2 to 30 μm. We used techniques of imaging based on light scattering perpendicular to the axis of the chain to visualize and study periodically focused beams in such structures. The results demonstrate good agreement with geometrical optics modeling for sufficiently large spheres, D>>10λ, where D is the sphere diameter and λ is the wavelength of light. For mesoscale structures with 4<D/>><10 we observed two effects which cannot be explained by geometrical optics. One is a "beam tapering" effect which is stronger in normalized units than it is theoretically possible in the limit of geometrical optics in short chains. Another effect is reduced power attenuation in sufficiently long chains which is found to be smaller than it is possible in the limit of geometrical optics. Both effects are ascribed to the increased role of physical optics properties. We can also suggest some role of the microjoints developing between polystyrene microspheres in self-assembled structures. The results are important for developing applications requiring focusing of multimodal beams such as mid-infrared laser surgery.

Paper Details

Date Published: 7 February 2012
PDF: 7 pages
Proc. SPIE 8236, Laser Resonators, Microresonators, and Beam Control XIV, 823622 (7 February 2012); doi: 10.1117/12.909467
Show Author Affiliations
Kenneth W. Allen, The Univ. of North Carolina at Charlotte (United States)
Arash Darafsheh, The Univ. of North Carolina at Charlotte (United States)
Vasily N. Astratov, The Univ. of North Carolina at Charlotte (United States)


Published in SPIE Proceedings Vol. 8236:
Laser Resonators, Microresonators, and Beam Control XIV
Alexis V. Kudryashov; Alan H. Paxton; Vladimir S. Ilchenko, Editor(s)

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