Observing inside the coronagraphic regime with optimized single-mode nulling interferometry

E. Serabyn; G. Ruane; D. Echeverri

doi:10.1117/12.2630589

27 August 2022 Observing inside the coronagraphic regime with optimized single-mode nulling interferometry

E. Serabyn, G. Ruane, D. Echeverri

Proceedings Volume 12180, Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave; 121800N (2022) https://doi.org/10.1117/12.2630589
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Abstract

The number of terrestrial exoplanets accessible to high-contrast coronagraphic imaging with large telescopes is limited by the smallest angular offset from bright stars at which coronagraphs can observe. However, it is possible to reach inside a telescope’s coronagraphic regime by employing nulling interferometry across a telescope’s pupil. Indeed, “cross-aperture” nulling interferometry can observe significantly closer to stars than typical coronagraphs, enabling observations even within the stellar diffraction core. Identifying an optimal nulling coronagraph, i.e., one with both a very small IWA and a high throughput for exoplanet light, would thus be of great interest. A systematic examination of available nulling options has therefore been carried out, which has led to three things. The first is a topological overview that unites both multiaperture nulling interferometers and single-aperture phase coronagraphs into a common geometrical framework. The second is a new type of phase-mask coronagraph that has emerged from a gap in this framework, called here the “splitring” coronagraph. The third is a clear identification of the optimal configuration for a nulling coronagraph, which turned out to be an aperture-plane phase knife, i.e., an achromatic π-radian phase shift applied to half the telescope pupil prior to focusing the telescope’s point spread function (PSF) into a single-mode fiber. The theoretical peak efficiency of the phaseknife fiber coronagraph, 35.2% for a circular telescope aperture, is found to be almost twice that of the next most efficient case, the vortex fiber nuller, at 19.0%.

Conference Presentation

Citation Download Citation

E. Serabyn, G. Ruane, and D. Echeverri "Observing inside the coronagraphic regime with optimized single-mode nulling interferometry", Proc. SPIE 12180, Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave, 121800N (27 August 2022); https://doi.org/10.1117/12.2630589

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