Extrasolar Planet Finding via Optimal Apodized‐Pupil and Shaped‐Pupil Coronagraphs

Kasdin, N. Jeremy; Vanderbei, Robert J.; Spergel, David N.; Littman, Michael G.

doi:10.1086/344751

Cited by 211 publications

(222 citation statements)

References 8 publications

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“…A binary design using a halftone-dot process can in principle be generalized to any apodizer masks (APLC, Dual zone) and even a conventional pupil apodization coronagraph (Jacquinot & Roisin-Dossier 1964;Nisenson & Papaliolios 2001;Aime 2005), or as an alternative manufacturing solution for binaryshaped pupil-coronagraph masks Kasdin et al 2003;Vanderbei et al 2004;Enya et al 2007Enya et al , 2008.…”

Section: Introductionmentioning

confidence: 99%

Design, analysis, and testing of a microdot apodizer for the Apodized Pupil Lyot Coronagraph

Martínez

Dorrer

Carpentier³

et al. 2008

A&A

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Context. Coronagraphic techniques are required for detecting exoplanets with future Extremely Large Telescopes. One concept, the Apodized Pupil Lyot Coronagraph (APLC), combines an apodizer in the entrance aperture with a Lyot opaque mask in the focal plane. This paper presents the manufacturing and testing of a microdots apodizer optimized for the near IR. Aims. We attempt to demonstrate the feasibility and performance of binary apodizers for the APLC. This study is also relevant to coronagraph using amplitude pupil apodization. Methods. A binary apodizer was designed using a halftone-dot process, where the binary array of pixels with either 0% or 100% transmission was calculated to fit the required continuous transmission, i.e. local transmission control was obtained by varying the relative density of the opaque and transparent pixels. An error-diffusion algorithm was used to optimize the distribution of pixels that approximated the required field transmission. The prototype was tested with a coronagraphic setup in the near IR. Results. The transmission profile of the prototype agrees with the theoretical shape to within 3% and is achromatic. The observed apodized and coronagraphic images are consistent with theory. However, binary apodizers introduce high frequency noise that is a function of the pixel size. Numerical simulations were used to specify pixel size and minimize this effect, and validated by experiment. Conclusions. This paper demonstrates that binary apodizers are well suited for use in high-contrast imaging coronagraphs. The correct choice of pixel size is important and must be addressed by considering the scientific field of view.

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Section: Introductionmentioning

confidence: 99%

Design, analysis, and testing of a microdot apodizer for the Apodized Pupil Lyot Coronagraph

Martínez

Dorrer

Carpentier³

et al. 2008

A&A

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“…They were more recently studied in detail for direct detection of exoplanets. Besides, numeric optimizations of coronagraphic problems can lead to various designs of pupil masks: shaped pupils, barcode masks, checkerboard masks, and other types of binary apodizers are described in Spergel & Kasdin (2001), Vanderbei et al (2003), and Kasdin et al (2003). These apodizers can provide very high contrasts and possess the advantage of having achromatic transmissions.…”

Section: Discussionmentioning

confidence: 99%

“…These concepts include external occulters (Cash 2006;Vanderbei et al 2007;Arenberg et al 2007), nuller interferometers (Bracewell 1978), various pupil apodization techniques (Nisenson & Papaliolios 2001;Kasdin et al 2003;Guyon 2003;Aime 2005), and coronagraphs (Gay & Rabbia 1996;Roddier & Roddier 1997;Rouan et al 2000;Mawet et al 2005;Guyon et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Reducing star leakage with a nuller coronagraph

Aimé

Rabbia

Carlotti

et al. 2011

A&A

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Aims. Our objective is to test the improvement of the detection capabilities of a nuller coronagraph when it is coupled to an apodizer. We call this instrument an apodized nuller coronagraph (ANC). Methods. With the usual Fourier optics formalism we first derive the analytical expression of the intensity distribution for an off-axis point-like source in the aperture and the focal plane of an ANC. Then the star leakage is obtained by integration of this response over the angular extension of the star. In this process are included the star's angular diameter, the apodization strength and the diameter of the telescope. Eventually we consider an application to the specific case of Sonine apodization. Results. From this analytical approach we obtain expressions of the contrast and signal-to-noise ratio for the direct detection of an exoplanet. These expressions involving instrumental parameters allow one to optimize the required minimum telescope's diameter and apodization strength with respect to the detection of a given target in spite of star leakage. We show that the direct detection of an exoplanet in a solar-like system can be obtained with a nuller coronagraph as soon as the aperture is sufficiently apodized, although the energy throughput of the system is reduced. For a system at 10 pc, an 8-m class telescope appears necessary to detect an exo-Earth, while no larger than a 2-m class telescope is required for an exo-Jupiter.

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“…The second one is to get rid of the need for a Lyot stop with the use of an optimized apodization that will concentrate the stellar light within the central peak, rather than eliminating it. Such an apodization is obtained either by multiplication of the entrance pupil with a smooth/continuous function (Nisenson & Papaliolios 2001;Gonsalves & Nisenson 2003;Aime 2005) or by using a shaped/binary pupil function (Kasdin et al 2003;Vanderbei et al 2003aVanderbei et al ,b, 2004Aime 2005). In this case, the diffraction rings of the stellar point spread function (PSF) are considerably reduced, resulting in higher contrast in the search area, but an opaque coronagraphic mask is still required to mask out the brighter central peak.…”

Section: Introductionmentioning

confidence: 99%

Apodization in high-contrast long-slit spectroscopy

Vigan

N’Diaye

Dohlen

2013

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The spectroscopy of faint planetary-mass companions to nearby stars is one of the main challenges that new-generation high-contrast spectro-imagers are going to face. However, the high contrast ratio between main-sequence stars and young planets makes it difficult to extract a companion spectrum that is not biased by the signal from the star. In a previous work we demonstrated that coupling long-slit spectroscopy (LSS) and classical Lyot coronagraphy (CLC) to form a long-slit coronagraph (LSC) allows low-mass companions to be properly characterized when combined with an innovative a posteriori data analysis methods based on the spectral deconvolution (SD). However, the presence of a slit in the coronagraphic focal plane induces a complex distribution of energy in the Lyot pupil plane that cannot be easily masked with a binary Lyot stop, creating strong diffraction residuals at close angular separation. To alleviate this concern, we propose to use a pupil apodization to suppress diffraction, creating an apodized long-slit coronagraph (ALSC). We show that this concept allows looking at a closer separation from the star, at deeper contrast, which enables the characterization of fainter substellar companions. After describing how the apodization was optimized, we demonstrate its advantages with respect to the CLC in the context of SPHERE/IRDIS LSS mode at low resolution with a 0.12 slit and 0.18 coronagraphic mask. We performed different sets of simulations with and without aberrations, and with and without a slit to demonstrate that the apodization is a more appropriate concept for LSS, at the expense of a significantly reduced throughput (37%) compared to the LSC. Then we performed detailed end-to-end simulations of the LSC and the ALSC that include realistic levels of aberrations to obtain several datasets representing 1 h of integration time on stars of spectral type A0 to M0 located at 10 pc. We inserted the spectra of planetary companions at different effective temperatures (T eff ) and surface gravities (log g) into the data at angular separations of 0.3 to 1.5 and with contrast ratios from 6 to 18 mag. Using the SD method to subtract the speckles, we show that the ALSC brings a gain in sensitivity of up to ∼3 mag at 0.3 over the LSC and that both concepts are essentially equivalent for separations larger than 0.5 . The gain at small separation is the result of suppressing of the bright Airy rings that are difficult to estimate at very small angular separations because of the point spread function chromaticity. The improved sensitivity is confirmed by extracting the simulated companions spectra from the data and comparing them to libraries of models to determine their T eff and log g. Using a restoration factor that quantitatively compares the input and output spectra, we show that the ALSC data systematically leads to better quality spectra below 0.5 . In terms of T eff , we demonstrate that at small angular separations the limit with the ALSC is always lower by at least 100 K, inducing an increase i...

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Extrasolar Planet Finding via Optimal Apodized‐Pupil and Shaped‐Pupil Coronagraphs

Cited by 211 publications

References 8 publications

Design, analysis, and testing of a microdot apodizer for the Apodized Pupil Lyot Coronagraph

Design, analysis, and testing of a microdot apodizer for the Apodized Pupil Lyot Coronagraph

Reducing star leakage with a nuller coronagraph

Apodization in high-contrast long-slit spectroscopy

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