Boosting dispersive spectrograph stability 1000x using an interferometer with crossfaded delays

David J. Erskine

doi:10.1117/12.2559219

13 December 2020 Boosting dispersive spectrograph stability 1000x using an interferometer with crossfaded delays

David J. Erskine

Proceedings Volume 11451, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV; 114512D (2020) https://doi.org/10.1117/12.2559219
Event: SPIE Astronomical Telescopes + Instrumentation, 2020, Online Only

Abstract

We demonstrate a key step along a technical route to achieving cm/s scale accuracy for astronomical spectrographs over long (multi-year) time scales, which is critical for the Doppler characterization of earth sized exoplanets, and measurement of small cosmic redshift drift over many years. This same technique is also en- abling for searching exoplanet atmospheres for biosignficant molecules in direct planet imaging using otherwise insufficiently low resolution and drift prone dispersive (grating or prism) spectrographs. Using a new method called crossfading" for externally dispersed interferometers (EDI) to get highly robust spectra, we recently demonstrated a factor of 1000x reduction in the net shift of an EDI measured ThAr line to a deliberate simulated wavelength translation of the detector. This 1000x gain in disperser stability can be combined with conventional stability gains afforded by fiber scramblers, vacuum tanks, and thermal control, to provide an additional 1 to 3 orders of magnitude reduction in the net PSF shift drift. Crossfading combines high and low delay fringing signals that react oppositely in phase to cancel their net reaction to a detector wavelength drift. This can be implemented by an interferometer addition to a facility spectrograph.

Conference Presentation

Citation Download Citation

David J. Erskine "Boosting dispersive spectrograph stability 1000x using an interferometer with crossfaded delays", Proc. SPIE 11451, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV, 114512D (13 December 2020); https://doi.org/10.1117/12.2559219

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