Modal noise mitigation in a photonic lantern fed near-IR spectrograph

Fraser A. Pike, Aurélien Benoit, David G. MacLachlan, Robert J. Harris, Itandehui Gris-Sánchez, David Lee, Timothy A. Birks, Robert R. Thomson

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

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Recently we have demonstrated the potential of a hybrid astrophotonic device, consisting of a multi-core fiber photonic lantern and a 3D waveguide reformatting component, to efficiently reformat the multimode point spread function of a telescope to a diffracted limited pseudo-slit. Here, we report on an investigation into the potential of this device to mitigate modal noise-one of the main hurdles of multi-mode fiber-fed spectrographs. The modal noise performance of the photonic reformatter and other fiber feeds was assessed using a bench-Top spectrograph based on an echelle grating. In a first method of modal noise quantification, we used broadband light as the input, and assessed the modal noise performance based on the variations in the normalized spectrum as the input coupling to the fiber feed is varied. In a second method, we passed the broadband light through an etalon to generate a source with spectrally narrow peaks. We then used the spectral stability of these peaks as the input coupling to the fiber feed was varied as a proxy for the modal noise. Using both of these approaches we found that the photonic reformatter could significantly reduce modal noise compared to the multi-mode fiber feed, demonstrating the potential of photonic reformatters to mitigate modal noise for applications such as near-IR radial velocity measurements of M-dwarf stars.

Original languageEnglish
Title of host publicationAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV
EditorsRamon Navarro, Roland Geyl
ISBN (Electronic)9781510636903
ISBN (Print)9781510636897
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
  • exoplanet detection
  • modal noise
  • photonic lanterns
  • radial velocity
  • spectrographs
  • ultrafast laser inscription
  • waveguides

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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