Beam tapering effect in microsphere chains: From geometrical to physical optics

Kenneth W. Allen, Arash Darafsheh, Vasily N. Astratov

Research output: Chapter in Book/Report/Conference proceedingConference contribution

5 Scopus citations

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/λ<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.

Original languageEnglish
Title of host publicationLaser Resonators, Microresonators, and Beam Control XIV
DOIs
StatePublished - Mar 6 2012
Externally publishedYes
EventLaser Resonators, Microresonators, and Beam Control XIV - San Francisco, CA, United States
Duration: Jan 22 2012Jan 25 2012

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Volume8236
ISSN (Print)1605-7422

Conference

ConferenceLaser Resonators, Microresonators, and Beam Control XIV
CountryUnited States
CitySan Francisco, CA
Period01/22/1201/25/12

Keywords

  • focusing
  • geometrical optics design
  • laser surgery
  • medical optics
  • microlens
  • microoptics
  • microspheres
  • ophthalmic optics and devices
  • optical microprobes

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    Allen, K. W., Darafsheh, A., & Astratov, V. N. (2012). Beam tapering effect in microsphere chains: From geometrical to physical optics. In Laser Resonators, Microresonators, and Beam Control XIV [823622] (Progress in Biomedical Optics and Imaging - Proceedings of SPIE; Vol. 8236). https://doi.org/10.1117/12.909467