Focusing capability of integrated chains of microspheres in the limit of geometrical optics

Arash Darafsheh, Kenneth W. Allen, Amir Fardad, Nathaniel M. Fried, Andrew N. Antoszyk, Howard S. Ying, Vasily N. Astratov

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

8 Scopus citations


The effects of periodical focusing of light were studied in chains of sapphire microspheres with 300 μm diameters assembled either on a substrate or inside capillary tubing. Dye-doped fluorescent microspheres were used as multimodal sources of light in experimental studies. Significant reduction of the focused spot sizes was observed for chains of spheres compared to a single sphere case. Numerical ray tracing simulations were performed for similar chains assembled inside hollow waveguides to be used as an optical delivery system with mid-infrared lasers for ultra-precise surgery. The device designs were optimized for contact conditions during laser surgery involving short optical penetration depths of light in tissue. It is shown that chains of spheres with n around 1.65-1.75 provide a two-fold improvement of the spatial resolution over single spheres. Potential applications of these microprobes include ultraprecise laser procedures in the eye and brain or piercing a cell, and coupling of multimodal beams into photonic microstructures.

Original languageEnglish
Title of host publicationLaser Resonators and Beam Control XIII
StatePublished - 2011
EventLaser Resonators and Beam Control XIII - San Francisco, CA, United States
Duration: Jan 23 2011Jan 25 2011

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


ConferenceLaser Resonators and Beam Control XIII
Country/TerritoryUnited States
CitySan Francisco, CA


  • Focusing
  • Geometrical optics design
  • Laser surgery
  • Medical optics
  • Microlens
  • Microoptics
  • Microspheres
  • Ophthalmic optics and devices
  • Optical microprobes


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