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Review

Roadmap for Exoplanet High-Contrast Imaging: Nulling Interferometry, Coronagraph, and Extreme Adaptive Optics

1
College of Biological and Agricultural Engineering, Jilin University, Changchun 130025, China
2
Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
3
School of Mechanical and Aerospace Engineering (SMAE), Jilin University, Changchun 130025, China
*
Authors to whom correspondence should be addressed.
Photonics 2025, 12(10), 1030; https://doi.org/10.3390/photonics12101030
Submission received: 21 August 2025 / Accepted: 3 October 2025 / Published: 17 October 2025

Abstract

The detection and characterization of exoplanets are central topics in astronomy, and high-contrast imaging techniques such nulling interferometry, coronagraphs, and extreme adaptive optics (ExAO) are key tools for the direct detection of exoplanets. This review synthesizes the pivotal role of these techniques in astronomical research and critically analyzes their role as key drivers of progress in the field. Nulling interferometry suppresses stellar light through the phase control of multiple telescopes, thereby enhancing the detection of faint planetary signals. This technology has evolved from the initial Bracewell concept to the LIFE (Large Interferometer For Exoplanets) technique, which will achieve a contrast ratio of 10−7 in the mid-infrared wavelength range in the future. Coronagraphs block starlight to create a “dark region” for direct observation of exoplanets. By leveraging innovative mask designs, theoretical contrast ratios of up to 4 × 10−9 can be achieved. ExAO systems achieve precise wavefront correction to optimize the high-contrast imaging performance and mitigate atmospheric disturbances. By leveraging wavefront sensing, thousand-element deformable mirrors, and real-time control algorithms, these systems suppress the turbulence correction residuals to 80 nm RMS, enabling ground-based telescopes to achieve a Strehl ratio exceeding 0.9. This work provides a comprehensive analysis of the underlying principles, prevailing challenges, and future application prospects of these technologies in astronomy.
Keywords: nulling interferometry; coronagraphs; extreme adaptive optics (ExAO); exoplanet exploration; high-contrast imaging techniques; imaging of terrestrial planets nulling interferometry; coronagraphs; extreme adaptive optics (ExAO); exoplanet exploration; high-contrast imaging techniques; imaging of terrestrial planets

Share and Cite

MDPI and ACS Style

Guo, Z.; An, Q.; Yang, C.; Hu, J.; Li, X.; Wang, L. Roadmap for Exoplanet High-Contrast Imaging: Nulling Interferometry, Coronagraph, and Extreme Adaptive Optics. Photonics 2025, 12, 1030. https://doi.org/10.3390/photonics12101030

AMA Style

Guo Z, An Q, Yang C, Hu J, Li X, Wang L. Roadmap for Exoplanet High-Contrast Imaging: Nulling Interferometry, Coronagraph, and Extreme Adaptive Optics. Photonics. 2025; 12(10):1030. https://doi.org/10.3390/photonics12101030

Chicago/Turabian Style

Guo, Ziming, Qichang An, Canyu Yang, Jincai Hu, Xin Li, and Liang Wang. 2025. "Roadmap for Exoplanet High-Contrast Imaging: Nulling Interferometry, Coronagraph, and Extreme Adaptive Optics" Photonics 12, no. 10: 1030. https://doi.org/10.3390/photonics12101030

APA Style

Guo, Z., An, Q., Yang, C., Hu, J., Li, X., & Wang, L. (2025). Roadmap for Exoplanet High-Contrast Imaging: Nulling Interferometry, Coronagraph, and Extreme Adaptive Optics. Photonics, 12(10), 1030. https://doi.org/10.3390/photonics12101030

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