An Eight-Octant Phase-Mask Coronagraph

Murakami, Naoshi; Uemura, Ryosuke; Baba, Naoshi; Nishikawa, Jun; Tamura, Motohide; Hashimoto, Nobuyuki; Abe, Lyu

doi:10.1086/592285

Cited by 59 publications

(37 citation statements)

References 26 publications

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“…For each position, we integrate the light inside a disk equal in size to the central part of the diffraction pattern after the Lyot stop. Our results are in accordance with the transmission maps calculated by Murakami et al (2008). In the same way as performed in their paper, we also define the mask's angular inner limitation to be the angular distance for which the planet's intensity decreases to half of its maximum value.…”

Section: Inner Working Anglessupporting

confidence: 88%

“…This approach also makes it possible to reproduce analytically the transmitted light in the entire re-imaged pupil plane. Generalizing the approach of Jenkins (2008) and Murakami et al (2008), a mask of k sectors can be written as the Fourier expansion…”

Section: Appendix A: Expected Null For the 8oc Inside The Aperture VImentioning

confidence: 99%

“…This condition may be relaxed with the eight-octant phase mask coronagraph (8OC), as shown by Murakami et al (2008). The main difficulty is chromaticity.…”

Section: Introductionmentioning

confidence: 99%

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Phase mask coronagraphy using a Mach-Zehnder interferometer

Carlotti

Ricort²,

Aime³

2009

A&A

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Aims. We report results obtained with a four-quadrant and an eight-octant phase-mask coronagraphs (4QC and 8OC) produced using amplitude masks inside a Mach-Zehnder interferometer (MZI). We describe the laboratory implementation of these coronagraphs operated in laser light and provide a detailed comparison between theory and experiment. Methods. The +1 and -1 (π phase) amplitude transmissions required to produce a 4QC or an 8OC were obtained using complementary binary-masks (transmission of 1 or 0 for quadrants of similar parities) in the two arms of a MZI, taking advantage of the achromatic π phase shift between the two paths. In one output of the MZI, the reconstructed image of the focal plane is similar to those obtained for sectorised phase-masks coronagraphs, and the image of the aperture corresponds to the characteristic patterns of the 4QC/8OC coronagraphs. Results. Observations are compared with the theory published by other authors and developed further here. The expressions for the light diffracted outside the aperture image are simplified using the Zernike radial polynomials Z 1 n instead of the rapidly diverging hypergeometric functions otherwise used. Experimental results are found to be in very good agreement with the theory. With the present laboratory experiment, about 99% of the light is rejected outside the Lyot stop and the contrast obtained beyond 5λ/D is higher than 10 5 for both the 4QC and 8OC. As expected, the 8OC is less affected by a pointing error than the 4QC, but more sensitive to an aperture central obstruction. Incidently, the loss of transmission for a planet crossing two phase masks is given theoretically as a function of the Lyot stop size, in agreement with observations.

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Section: Inner Working Anglessupporting

confidence: 88%

Section: Appendix A: Expected Null For the 8oc Inside The Aperture VImentioning

confidence: 99%

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Phase mask coronagraphy using a Mach-Zehnder interferometer

Carlotti

Ricort²,

Aime³

2009

A&A

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“…Many kinds of focal-plane phase masks have been proposed to date, such as four-quadrant phase mask (4QPM), eight-octant phase mask (8OPM), and optical or vector vortex masks (Rouan et al 2000;Murakami et al 2008;Foo et al 2005;Mawet et al 2005). These phase masks will realize perfect stellar elimination, assuming that a telescope pupil does not have a central obscuration.…”

Section: Phase-mask Coronagraph With Centrally-obscured Telescope Pupilmentioning

confidence: 99%

Central-Obscuration Removal Plates for Focal-Plane Phase-Mask Coronagraphs with a Centrally-Obscured Telescope

Oshiyama¹,

Murakami²,

Guyon³

et al. 2014

Publications of the Astronomical Society of the Pacific

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ABSTRACT. Focal-plane phase-mask coronagraphs, such as eight-octant phase-mask coronagraphs (8OPM), are one of the most promising tools for high contrast observations. However, coronagraphic performance would be degraded when combined with a centrally-obscured telescope. We propose pupil-remapping optics for removing the shade of a secondary mirror to generate a clear, circular pupil for the phase-mask coronagraph. First, we show the design of the pupil-remapping optics, called central-obscuration removal plates (CRPs). Next, we report laboratory experiments on the 8OPM coronagraph using manufactured CRPs. We also evaluate off-axis point-spread functions via both laboratory experiments and numerical simulations. Finally, we evaluate, via numerical simulations, limiting factors for coronagraphic performance, such as phase aberrations introduced by the CRPs, the effect of Fresnel diffraction, and chromatic behavior. The numerical simulations suggest that the phase aberrations could be a dominant limiting factor of the achievable contrast in the current laboratory experiments.

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“…To improve the detection in the presence of star leakage, Tavrov et al (2008) proposed using a nulling out-of-plane coronagraph with two common-path interferometers in tandem. We note that this is a common problem for many coronagraphs, and for the same objective of reducing star leakage the use of eight octants phase masks was proposed by Murakami et al (2008) instead of the original four quadrant phase mask of Rouan et al (2000).…”

Section: Introductionmentioning

confidence: 99%

ARC: an Achromatic Rotation-shearing Coronagraph

Aime¹,

Ricort²,

Carlotti

et al. 2010

A&A

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Context. Because of the larger size of future telescopes, the star leakage effect due to the finite diameter of the stars will become a major problem for coronagraphs with very small inner working angles (IWA). Aims. To reduce this star leakage, we propose a new instrumental concept, the Achromatic Rotation-shearing Coronagraph (ARC), that provides a variable IWA that is easily tunable to ensure the observation of Solar-like systems with an extremely large telescope. Methods. The ARC belongs to the nuller class of coronagraphs. It takes advantage of the achromatic dark output of a Mach-Zehnder interferometer (MZI). Field rotators set in the arms of the MZI rotate the π-phase shifted images of the MZI by an angle ψ. An on-axis point source (the star) is nulled as twin-images of an off-axis point source (the planet) are formed. For ψ = π, the ARC is equivalent to the achromatic interfero-coronagraph. For small ψ, the twin images of the off-axis source are formed close to each another, and eventually nulled if too close. In this way, the ARC can get rid of star leakage while optimizing the transmission of the planet. We describe the compensation of polarization effects induced by field rotators. An application to diluted apertures is shortly presented. Results. We perform the mathematical analysis of the technique using Cartesian and polar coordinates, and assuming that the system is optically perfect. Analytic expressions are given for the leakage in both the focal and aperture planes. Simplified expressions for the contrast and signal-to-noise ratio (SNR) in the focal plane are given for a circular aperture, explicitly showing that the level of star leakage decreases as sin 2 (ψ/2), while the SNR increases as the inverse of sin(ψ/2). Conclusions. The ARC is appropriate for the detection of exoplanets and is not intended to provide images of the environment of stars.

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An Eight-Octant Phase-Mask Coronagraph

Cited by 59 publications

References 26 publications

Phase mask coronagraphy using a Mach-Zehnder interferometer

Phase mask coronagraphy using a Mach-Zehnder interferometer

Central-Obscuration Removal Plates for Focal-Plane Phase-Mask Coronagraphs with a Centrally-Obscured Telescope

ARC: an Achromatic Rotation-shearing Coronagraph

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