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Title: Suppression of fiber modal noise induced radial velocity errors for bright emission-line calibration sources

Modal noise in optical fibers imposes limits on the signal-to-noise ratio (S/N) and velocity precision achievable with the next generation of astronomical spectrographs. This is an increasingly pressing problem for precision radial velocity spectrographs in the near-infrared (NIR) and optical that require both high stability of the observed line profiles and high S/N. Many of these spectrographs plan to use highly coherent emission-line calibration sources like laser frequency combs and Fabry-Perot etalons to achieve precision sufficient to detect terrestrial-mass planets. These high-precision calibration sources often use single-mode fibers or highly coherent sources. Coupling light from single-mode fibers to multi-mode fibers leads to only a very low number of modes being excited, thereby exacerbating the modal noise measured by the spectrograph. We present a commercial off-the-shelf solution that significantly mitigates modal noise at all optical and NIR wavelengths, and which can be applied to spectrograph calibration systems. Our solution uses an integrating sphere in conjunction with a diffuser that is moved rapidly using electrostrictive polymers, and is generally superior to most tested forms of mechanical fiber agitation. We demonstrate a high level of modal noise reduction with a narrow bandwidth 1550 nm laser. Our relatively inexpensive solution immediately enables spectrographs tomore » take advantage of the innate precision of bright state-of-the art calibration sources by removing a major source of systematic noise.« less
Authors:
; ; ;  [1]
  1. Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)
Publication Date:
OSTI Identifier:
22357037
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 786; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; CALIBRATION; COUPLING; DIFFUSERS; EMISSION; INHIBITION; MASS; NEAR INFRARED RADIATION; NOISE; OPTICAL FIBERS; PLANETS; RADIAL VELOCITY; REDUCTION; SIGNAL-TO-NOISE RATIO; SPHERES; STABILITY; VISIBLE RADIATION; WAVELENGTHS