K-band integrated optics beam combiners for CHARA fabricated by ultrafast laser inscription

Fraser A. Pike*, Tarun K. Sharma, Aurélien Benoît, David G. MacLachlan, Aline N. Dinkelaker, Abani S. Nayak, Kalaga Madhav, Martin M. Roth, Lucas Labadie, Ettore Pedretti, Theo A. ten Brummelaar, Nicholas J. Scott, Vincent Coudé Du Foresto, Robert R. Thomson

*Corresponding author for this work

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

1 Citation (Scopus)
100 Downloads (Pure)


We report the ultrafast laser inscription (ULI) and characterization of 3 dB directional achromatic couplers for K-band between 2 and 2.4 μm. The couplers were fabricated in commercial Infrasil glass using 1030 nm femtosecond laser pulses. Straight waveguides inscribed using optimal fabrication parameters exhibit an average propagation loss of ~1.21 dB over full range of K-band with a single-mode behavior for a length of 17 mm. Directional couplers with different interaction lengths and waveguide widths were fabricated and characterized. We demonstrate that 3 dB achromatic directional couplers for K-band can be fabricated using ULI. These results show that ULI can fabricate highquality couplers for future applications in astronomical interferometry. Our eventual aim is to develop a two-telescope K-band integrated optical beam combiner to replace JouFLU at CHARA.

Original languageEnglish
Title of host publicationOptical and Infrared Interferometry and Imaging VII
EditorsPeter G. Tuthill, Antoine Merand, Stephanie Sallum
ISBN (Electronic)9781510636804
ISBN (Print)9781510636798
Publication statusPublished - 13 Dec 2020
EventSPIE Astronomical Telescopes + Instrumentation 2020 - Virtual, Online, United States
Duration: 14 Dec 202022 Dec 2020

Publication series

NameProceedings of SPIE
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceSPIE Astronomical Telescopes + Instrumentation 2020
Country/TerritoryUnited States
CityVirtual, Online


  • Astrophotonics
  • Beam combiner
  • Integrated optics
  • Long-baseline interferometry
  • Ultrafast laser inscription

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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