Experimental demonstration of a dark hole at the diffraction limit
5 affiliations
- 1Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange
- 2Steward Observatory, University of Arizona
- 3Astrobiology Center, National Institutes of Natural Sciences
- 4National Astronomical Observatory of Japan, Subaru Telescope, National Institutes of Natural Sciences
- 5Centre National d’Etudes Spatiales
Abstract
Context. High-contrast imaging at very small angular separations is essential for detecting and characterizing exoplanets orbiting close to their host stars. Future segmented telescopes will play a key role in direct exoplanet imaging by enabling the large apertures required to achieve high angular resolution and sensitivity. However, their complex pupils introduce challenging diffraction effects.
Aims. We experimentally demonstrate the formation of a dark hole (DH) at the diffraction limit on a segmented pupil.
Methods. Experiments were conducted on the SPEED test bed, a high-contrast imaging platform reproducing the diffraction environment of segmented apertures with a small inner working angle coronagraph. The setup implements a novel multi-deformable mirror (DM) architecture, in which two widely separated out-of-pupil DMs provide efficient amplitude and phase control at the diffraction limit. Focal-plane wavefront control was performed using implicit electric field conjugation (iEFC).
Results. We demonstrate a stable DH from 1 to 4 λ / D in the H band, providing, to our knowledge, the first experimental validation of diffraction-limited DH formation reaching 1 λ / D . Beyond this achievement, the demonstration is performed on a segmented telescope, representing the first realization of a diffraction-limited DH with a segmented pupil and iEFC focal-plane wavefront control.
Conclusions. Wavefront control and shaping down to 1 λ / D is challenging because of the PSF-core proximity and increased sensitivity to various factors. Rather than claiming record contrast or superiority over conventional DMs, this work validates the proposed two-DM architecture for close-in DH control on a segmented aperture, advancing the technology readiness of two-DM DH generation.
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BibTeX
@article{sallard2026experimental,
title = {{Experimental demonstration of a dark hole at the diffraction limit}},
author = {C. Sallard and P. Martinez and K. Milani and A. Spang and M. Beaulieu and C. Gouvret and J. Dejonghe and A. Marcotto and L. Abe and O. Guyon and O. Preis and J. M. Le Duigou},
journal = {Astronomy \& Astrophysics},
year = {2026},
month = oct,
doi = {10.1051/0004-6361/202662297},
url = {https://www.aanda.org/10.1051/0004-6361/202662297},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Experimental demonstration of a dark hole at the diffraction limit
AU - C. Sallard
AU - P. Martinez
AU - K. Milani
AU - A. Spang
AU - M. Beaulieu
AU - C. Gouvret
AU - J. Dejonghe
AU - A. Marcotto
AU - L. Abe
AU - O. Guyon
AU - O. Preis
AU - J. M. Le Duigou
PY - 2026
DA - 2026/10/20
JO - Astronomy & Astrophysics
DO - 10.1051/0004-6361/202662297
UR - https://www.aanda.org/10.1051/0004-6361/202662297
AB - Context. High-contrast imaging at very small angular separations is essential for detecting and characterizing exoplanets orbiting close to their host stars. Future segmented telescopes will play a key role in direct exoplanet imaging by enabling the large apertures required to achieve high angular resolution and sensitivity. However, their complex pupils introduce challenging diffraction effects. Aims. We experimentally demonstrate the formation of a dark hole (DH) at the diffraction limit on a segmented pupil. Methods. Experiments were conducted on the SPEED test bed, a high-contrast imaging platform reproducing the diffraction environment of segmented apertures with a small inner working angle coronagraph. The setup implements a novel multi-deformable mirror (DM) architecture, in which two widely separated out-of-pupil DMs provide efficient amplitude and phase control at the diffraction limit. Focal-plane wavefront control was performed using implicit electric field conjugation (iEFC). Results. We demonstrate a stable DH from 1 to 4 λ / D in the H band, providing, to our knowledge, the first experimental validation of diffraction-limited DH formation reaching 1 λ / D . Beyond this achievement, the demonstration is performed on a segmented telescope, representing the first realization of a diffraction-limited DH with a segmented pupil and iEFC focal-plane wavefront control. Conclusions. Wavefront control and shaping down to 1 λ / D is challenging because of the PSF-core proximity and increased sensitivity to various factors. Rather than claiming record contrast or superiority over conventional DMs, this work validates the proposed two-DM architecture for close-in DH control on a segmented aperture, advancing the technology readiness of two-DM DH generation.
SN - 0004-6361
SN - 1432-0746
ER -