The evanescent wave coronagraph project: setup results and demonstrator preliminary design

Buisset, Christophe; Lépine, Thierry; Thiébaut, Éric; Langlois, M.; Tallon, Michel; Alagao, Mary Angelie; Tallon–Bosc, I.; Rabbia, Yves; Poshyachinda, S.; Soonthornthum, Boonrucksar; Ducrot, Elsa

doi:10.1117/12.2311958

Cited by 8 publications

(10 citation statements)

References 5 publications

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“…In the R-and V-band, we notice that the IWA is close to 4 λC/ Dmaj (respectively, close to 5 λC/ Dmaj in the V-band) instead of 3 λC/Dmaj in the I-band. This spectral variation of the IWA value is attributed to the contact area between the prism and the lens that constitute the coronagraphic mask as fully discussed in a previous paper [5]. We also notice that in both the R-and V-Band, the contrast varies between a few 10 -6 to a few 10 -7 at distances comprised between the IWA and 10 Airy radii from the PSF center.…”

Section: Icso 2018 International Conference On Space Opticssupporting

confidence: 71%

“…In 2016, NARIT and IOGS/LabHC have developed a testbed to demonstrate the concept of EvWaCo. This testbed has been presented in previous communication [3][4] [5] and is similar to the schematic presented in Figure 1. The only difference is that the DM is replaced by a plane mirror.…”

Section: Evwaco Testbed Performancementioning

confidence: 99%

“…Figure 2 shows the irradiance distribution of the star and a companion that is 3.10 4 fainter at 15 λC/D (top panel), and 10 5 fainter at 30 λC/D from the star PSF center (bottom panel). During these measurements, the star source emits an unpolarized light over the Johnson-Cousins photometric I-band which is centered on the wavelength λC ≈ 800 nm with a spectral ratio ∆λ/λC ≈ 20% [5]. The companion source is a LED emitting at the wavelength λ = 780 nm with a spectral ratio ∆λ/λC ≈ 3%.…”

Section: Evwaco Testbed Performancementioning

confidence: 99%

“…The WFS is specified to have 13 x 13 microlenses and the WFS detector will provide at least 7 pixels per micro lens PSF. A full description of the adaptive optics specifications can be found in [5].…”

Section: Prototype Design and Theoretical Performancementioning

confidence: 99%

“…We have developed a model of the EvWaCo companion channel to calculate the irradiance distribution in the image plane and the pupil planes by performing a succession of Fast Fourier Transforms. This model has been fully described in a previous communication [5]. In this section, we present the theoretical performance of EvWaCo obtained with the following assumptions: i) the IWA is equal to 3 λ/D, ii) the pupil is elliptical and apodized with a Gaussian function of Full Width at Half Maximum (FWHM) adjusted to reach a transmission equal to 5% at the edges of the pupil and iii) Lyot stop diameter equal to 78% of the exit pupil diameter.…”

Section: Theoretical Contrast Performancementioning

confidence: 99%

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The evanescent wave coronagraph project: development status and potential for space based observations

Alagao

Buisset

Lépine³

et al. 2019

International Conference on Space Optics — ICSO 2018

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The Evanescent Wave Coronagraph (EvWaCo) is a coronagraph with an occulting mask based on the frustration of total internal reflection to i) produce an achromatic extinction of the central star and ii) reveal the faint companion surrounding the star. Results obtained in laboratory conditions show contrast performance of a few 10-6 between 10 λC/D and 20 λC/D over the full I-band centered at the wavelength λC = 800 nm with a spectral ratio of ∆λ/ λC ≈ 20% in unpolarized light. In this paper, we discuss the advantages of using EvWaCo to observe and characterize exoplanets with a space-based telescope. In the first section, we describe the system and present the current results obtained with the EvWaCo testbed. We also illustrate the capability of this coronagraph to detect the companion 30,000 times (respectively, 100,000 times) fainter than the central star at distances equal to 15 Airy radii (respectively, 30 Airy radii) from the PSF center in polychromatic and unpolarized light. In the second section, we describe the design of the prototype dedicated to the on-sky tests of the instrument with the 2.4 m Thai National Telescope at horizon 2020. This prototype has been designed with the objective to reach a contrast equal to a few 10-4 at the inner working angle (IWA) equal to 3 λ/D from the star PSF center while observing through the atmosphere over the full photometric I-band. This prototype will include an adaptive optics specified to reach at λ ≈ 800 nm a Strehl ratio > 0.8 for magnitude m < 7. In the third section, we show the theoretical performance of EvWaCo: a contrast comprised between a few 10-6 and 10-7 in the I-Band between 3 λ/D and 10 λ/D in the I-Band for an IWA equal to 3 λ/D with a Gaussian apodization in unpolarized light. We also show that similar contrasts performance are obtained in the V-, R-, bands, thus illustrating the EvWaCo quasi-achromaticity. Finally, we discuss the advantages and the limitation using the proposed concept for space-based observations and spectral characterization of exoplanets.

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Section: Icso 2018 International Conference On Space Opticssupporting

confidence: 71%

Section: Evwaco Testbed Performancementioning

confidence: 99%

Section: Evwaco Testbed Performancementioning

confidence: 99%

Section: Prototype Design and Theoretical Performancementioning

confidence: 99%

Section: Theoretical Contrast Performancementioning

confidence: 99%

See 3 more Smart Citations

The evanescent wave coronagraph project: development status and potential for space based observations

Alagao

Buisset

Lépine³

et al. 2019

International Conference on Space Optics — ICSO 2018

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Analytical modelling of adaptive optics systems: Role of the influence function

Berdeu¹,

Tallon²,

Thiébaut³

et al. 2023

A&A

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Context. Adaptive optics (AO) is now a tool commonly deployed in astronomy. The real time correction of the atmospheric turbulence that AO enables allows telescopes to perform close to the diffraction limit at the core of their point spread function (PSF). Among other factors, AO-corrected PSFs depend on the ability of the wavefront corrector (WFC), generally a deformable mirror, to fit the incident wavefront corrugations. Aims. In this work, we focus on this error introduced by the WFC, the so-called fitting error. To date, analytical models only depend on the WFC cut-off frequency, and Monte Carlo simulations are the only solution for studying the impact of the WFC influence function shape on the AO-corrected PSF. We aim to develop an analytical model accounting for the influence function shape. Methods. We first obtain a general analytical model of the fitting error structure function. With additional hypotheses, we then derive an analytical model of the AO-corrected power spectral density (PSD). These two analytical solutions are compared with Monte Carlo simulations on different ideal profiles (piston, pyramid, Gaussian) as well as with real hardware (DM192 from ALPAO). Results. Our analytical predictions show a very good agreement with the Monte Carlo simulations. We show that in the image plane, the depth of the correction as well as the transition profile between the AO-corrected area and the remaining turbulent halo depend on the influence functions of the WFC. We also show that the generally assumed hypothesis of stationarity of the AO correction is actually not met. Conclusions. As the fitting error is the intrinsic optimal limit of an AO system, our analytical model allows for the assessment of the theoretical limits of extreme AO systems limited by the WFC in high-contrast imaging through a context where other errors become comparable.

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Multi-physical quantity sensing based on magnetized plasma spherical photonic crystals with evanescent wave

Xu,

Zhu,

Zhang

2023

J. Phys. D: Appl. Phys.

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In this paper, a novel structure of magnetized plasma spherical photonic crystals is proposed that enables the development of sensors based on the evanescent wave principle. This sensor structure integrates a plasma with two isotropic media and applies periodic boundary conditions. Leveraging the principle of the evanescent wave, when the incident light is perpendicular to the interface of a medium with high optical density or thickness and the incident angle exceeds a critical angle, the transfer matrix method is utilized to compute the sharp peaks in the transmission spectrum. Subsequently, sensors produced using these sharp absorption peaks can detect the magnetic induction intensity, plasma frequency, and solution concentration of serum creatinine. The sensitivity and quality factors of these measurements are 8.35×1010 T-1, 3583, 1.5×10-4 (2πc/d)-1, 2970, 3.55, and 22824, respectively. Furthermore, a detection limit of 9.15502×10-6 RIU should be taken into account to ensure the normal operation of serum creatinine detection, satisfying the minimum requirements of biosensing.

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The evanescent wave coronagraph project: setup results and demonstrator preliminary design

Cited by 8 publications

References 5 publications

The evanescent wave coronagraph project: development status and potential for space based observations

The evanescent wave coronagraph project: development status and potential for space based observations

Analytical modelling of adaptive optics systems: Role of the influence function

Multi-physical quantity sensing based on magnetized plasma spherical photonic crystals with evanescent wave

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