Towards freeform microlens arrays for near infrared astronomical instruments

D. Choudhury*, A. Arriola, J. R. Allington-Smith, C. Cunningham, R. R. Thomson

*Corresponding author for this work

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

6 Citations (Scopus)


A key requirement for astronomical instruments in next generation Extremely Large Telescopes (ELTs) is the development of large-aperture Integral Field Units (IFUs) that enable the efficient and spatially contiguous sampling of the telescope image plane for coupling stellar light onto a spectrometer. Current IFUs are complex to fabricate and suffer from stray light issues, which limits their application in high-contrast studies such as exoplanet imaging. In this paper, we present our work on the development of freeform microlens arrays using the rapidly maturing technique of ultrafast laser inscription and selective wet chemical etching. Using the focus spot from a femtosecond laser source as a tool with an essentially unrestricted "tool-path", we demonstrate that it is possible to directly write the surface of a lenslet in three dimensions within the volume of a transparent material. We further show that high surface quality of the lenses can be achieved by using an oxy-natural gas flame to polish the lens surface roughness that is characteristic of the post-etched structures. Using our technique, the shape and position of each lenslet can be tailored to match the spatial positioning of a two-dimensional multimode fiber array, which can be monolithically integrated with the microlens array.

Original languageEnglish
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
ISBN (Print)9780819496195
Publication statusPublished - 2014
EventAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation - Montreal, United Kingdom
Duration: 23 Jun 201427 Jun 2014


ConferenceAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation
Country/TerritoryUnited Kingdom


  • Femtosecond
  • Integral field unit
  • Microlens array
  • Selective etching
  • Ultrafast laser inscription


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