Experimental comparison of model-free and model-based dark hole algorithms for future space telescopes

Desai, Niyati; Potier, Axel; Ruane, Garreth; Poon, Phillip K.; Riggs, A.J.; Noyes, Matthew; Mejia Prada, Camilo

doi:10.1117/12.2677040

Cited by 3 publications

(1 citation statement)

References 28 publications

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“…A comparison between iEFC, SCC+EFC, and PWP+EFC showed similar performance (≃ 10 −8 ) with a vector vortex coronagraph (VVC). 27 In this work, we propose an algorithm based on iEFC to minimize the speckles coupling into an SMF for both ground-and space-based systems. In Sec.…”

Section: Introductionmentioning

confidence: 99%

Implicit electric field conjugation through a single-mode fiber

Liberman,

Llop-Sayson,

Bertrou-Cantou

et al. 2024

J. Astron. Telesc. Instrum. Syst.

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Connecting a coronagraph instrument to a spectrograph via a single-mode optical fiber is a promising technique for characterizing the atmospheres of exoplanets with ground and space-based telescopes. However, due to the small separation and extreme flux ratio between planets and their host stars, instrument sensitivity will be limited by residual starlight leaking into the fiber. To minimize stellar leakage, we must control the electric field at the fiber input. Implicit electric field conjugation (iEFC) is a model-independent wavefront control (WFC) technique in contrast with classical EFC, which requires a detailed optical model of the system. We present here the concept of an iEFC-based WFC algorithm to improve stellar rejection through a single-mode fiber (SMF). As opposed to image-based iEFC, which relies on minimizing intensity in a dark hole region, our approach aims to minimize the amount of residual starlight coupling into an SMF. We present broadband simulation results demonstrating a normalized intensity ≥10 −10 for both fiber-based EFC and iEFC. We find that both control algorithms exhibit similar performance for the low wavefront error (WFE) case, however, iEFC outperforms EFC by ≈100x in the high WFE regime. Having no need for an optical model, this fiber-based approach offers a promising alternative to EFC for ground and space-based telescope missions, particularly in the presence of residual WFE.

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Section: Introductionmentioning

confidence: 99%

Implicit electric field conjugation through a single-mode fiber

Liberman,

Llop-Sayson,

Bertrou-Cantou

et al. 2024

J. Astron. Telesc. Instrum. Syst.

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Comparative laboratory study of electric field conjugation algorithms

Desai,

Potier,

Redmond

et al. 2024

J. Astron. Telesc. Instrum. Syst.

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Future space telescope coronagraph instruments hinge on the integration of highperformance masks and precise wavefront sensing and control techniques to create dark holes essential for exoplanet detection. Recent advancements in wavefront control algorithms might exhibit differing performances depending on the coronagraph used. This research investigates three model-free and model-based algorithms in conjunction with either a vector vortex coronagraph or a scalar vortex coronagraph under identical laboratory conditions: pairwise probing with electric field conjugation, the self-coherent camera with electric field conjugation, and implicit electric field conjugation. We present experimental results in narrowband and broadband light from the In-Air Coronagraph Testbed at the Jet Propulsion Laboratory. We find that model-free dark hole digging methods achieve broadband contrasts comparable to model-based methods, and we highlight the calibration costs of model-free methods compared with model-based approaches. This study also reports the first time that electric field conjugation with the self-coherent camera has been applied for simultaneous multi-subband correction with a field stop. This study compares the advantages and disadvantages of each of these wavefront sensing and control algorithms with respect to their potential for future space telescopes.

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Metasurface-based scalar vortex phase mask in pursuit of 1e-10 contrast

König,

Palatnick,

Desai

et al. 2023

Techniques and Instrumentation for Detection of Exoplanets XI

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Imaging Earth-like planets around sun-like stars has become one of the main science drivers for future space telescope missions. High-contrast imaging using a vortex coronagraph has proven to be a promising approach for achieving this goal. However, at the huge contrast levels required for future space-based telescopes the vectorial nature of the well-established vector vortex phase mask becomes a limiting factor, since it imprints phase ramps of opposite signs on the two circular polarizations. An alternative polarization-independent approach is using a scalar vortex phase mask, which affects both polarizations in the same way. The achromatic performance of scalar vortex phase masks for space-based applications has still to be improved, though. Metasurfaces provide a promising approach to implement a scalar vortex phase mask with relatively simple fabrication techniques. Their demonstrated ability to implement broadband phase and amplitude masks makes them a prime candidate for achieving achromatic performance in pursuit of the 10−10 contrast limit required by NASA’s Habitable Worlds Observatory. We present a metasurface-based design of a scalar vortex phase mask providing a helical phase ramp across a large bandwidth. We first use rigorous coupled-wave analysis to create a library of square metasurface building blocks (nanoblocks) and choose an optimal set of nanoblock sizes providing broadband 2π phase coverage at a given nanoblock height. We then arrange the nanoblocks in a design providing a helical phase ramp and propagate the phase and transmission provided by the mask through a wavefront propagation software to obtain contrast curves at several wavelengths. Finally we apply electric field conjugation to dig a half-sided dark hole from 3-10 λ/D reaching 3.7 × 10−9 contrast in 20% bandwidth.

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Experimental comparison of model-free and model-based dark hole algorithms for future space telescopes

Cited by 3 publications

References 28 publications

Implicit electric field conjugation through a single-mode fiber

Implicit electric field conjugation through a single-mode fiber

Comparative laboratory study of electric field conjugation algorithms

Metasurface-based scalar vortex phase mask in pursuit of 1e-10 contrast

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