Topological designs for scalar vortex coronagraphs

Desai, Niyati; Llop-Sayson, Jorge; Bertrou-Cantou, Arielle; Ruane, Garreth; Riggs, A. J. Eldorado; Serabyn, Eugene; Mawet, Dimtiri

doi:10.1117/12.2630950

Cited by 9 publications

(22 citation statements)

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“…For the implementation of a scalar vortex with the present metasurface framework, a sawtooth vortex design featuring six 2π phase jumps is chosen. 26 This choice is motivated by the limited phase coverage that can be achieved with a nanoblock framework. The sawtooth design needs only 2π phase coverage, while a classical vortex needs 6 • 2π = 12π coverage.…”

Section: Optimizing For Broadband Performancementioning

confidence: 99%

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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Section: Optimizing For Broadband Performancementioning

confidence: 99%

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

View full text Add to dashboard Cite

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“…The focus of this paper is to provide a direct comparison for the wrapped staircase scalar vortex phase mask. However, Desai et al 28 . considered the simulated performance of an additional charge 6 variation of the phase wrapping design derived from that of Ref.…”

Section: Simulations Of Mask Topographiesmentioning

confidence: 99%

“…Odd modes, on the other hand, correspond to odd charged vortexes, where starlight suppression is deficient since only an even charge produces a null for a vortex coronagraph 5 – 8 This explains why the classical vortex, which displays odds modes in the modal decomposition (orange), exhibits the worst contrast performance in FALCO simulations 28 …”

Section: Simulations Of Mask Topographiesmentioning

confidence: 99%

Laboratory demonstration of the wrapped staircase scalar vortex coronagraph

Desai

Ruane

Llop-Sayson

et al. 2023

J. Astron. Telesc. Instrum. Syst.

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.Of the over 5000 exoplanets that have been detected, only about a dozen have ever been directly imaged. Earth-like exoplanets are on the order of 10 billion times fainter than their host star in visible and near-infrared, requiring a coronagraph instrument to block primary starlight and allow for the imaging of nearby orbiting planets. In the pursuit of direct imaging of exoplanets, scalar vortex coronagraphs (SVCs) are an attractive alternative to vector vortex coronagraphs (VVCs). VVCs have demonstrated 2 × 10 − 9 raw contrast in broadband light but have several limitations due to their polarization properties. SVCs imprint the same phase ramp as VVCs on the incoming light and do not require polarization splitting, but they are inherently chromatic. Discretized phase ramp patterns such as a wrapped staircase help reduce SVC chromaticity and simulations show it outperforms a chromatic classical vortex in broadband light. We designed, fabricated, and tested a wrapped staircase SVC, and here we present the broadband characterization on the high contrast spectroscopy testbed. We also performed wavefront correction on the in-air coronagraph testbed at NASA’s Jet Propulsion Laboratory and achieved an average raw contrasts of 3.2 × 10 − 8 in monochromatic light and 2.2 × 10 − 7 across a 10% bandwidth.

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“…At wavelengths offset from the design central wavelength, the zeroeth order leakage becomes a limiting factor in contrast performance. 9 Efforts towards achromatizing SVC designs include varying the FPM surface topography, combining two materials of different refractive indices into a dual-layer FPM, or employing metasurfaces optimized for broadband phase control. 7,8,[11][12][13] These two implementations offer opposite advantages and disadvantages in the trade-off between polarization insensitivity and achromaticity; both of which are important factors of consideration for a future space telescope coronagraph instrument.…”

Section: Scalar Vs Vector Vortex Masksmentioning

confidence: 99%

“…Although the VVC has so far demonstrated better contrast levels in the lab, ongoing SVC design and testing has shown it has potential to reach comparable performance. 8,9 To better inform the design of future space telescopes, a systematic comparison between available technologies needs to be conducted. Two key components, which are the focus of this study, include the choice of focal plane mask, and the wavefront sensing and control algorithm.…”

Section: Introductionmentioning

confidence: 99%

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

Desai,

Potier,

Ruane

et al. 2023

Techniques and Instrumentation for Detection of Exoplanets XI

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Coronagraphic instruments provide a great chance of enabling high contrast spectroscopy for the pursuit of finding a habitable world. Future space telescope coronagraph instruments require high performing focal plane masks in combination with precise wavefront sensing and control techniques to achieve dark holes for planet detection. Several wavefront control algorithms have been developed in recent years that might vary in performance depending on the coronagraph they are paired with. This study compares three model-free and model-based algorithms when coupled with either a Vector (VVC) or a Scalar (SVC) Vortex Coronagraph mask in the same 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 from the In-Air Coronagraph Testbed (IACT) at JPL in narrowband and broadband light, comparing the pros and cons of each of these wavefront sensing and control algorithms with respect to their potential for future space telescopes.

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Topological designs for scalar vortex coronagraphs

Cited by 9 publications

References 0 publications

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

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

Laboratory demonstration of the wrapped staircase scalar vortex coronagraph

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

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