Experimental demonstration of a dark hole at the diffraction limit
Year: 2026
Type: article
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.
Source: Astronomy and Astrophysics
Institutions: Centre National de la Recherche Scientifique, Université Côte d'Azur, Lagrange Laboratory, Observatoire de la Côte d’Azur, University of Arizona, National Institutes of Natural Sciences, Astrobiology Center, National Astronomical Observatory of Japan, Centre National d'Études Spatiales
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7215088159