Homothetic apodization of circular aperture HACA: simulation results

Azagrouze, O.; Habib, A.; Elazhari, Y.; Benkhaldoun, Z.; Lazrek, M.

doi:10.1117/12.856383

SPIE Proceedings

2010

DOI: 10.1117/12.856383

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Homothetic apodization of circular aperture HACA: simulation results

O. Azagrouze

A. Habib

Y. Elazhari

et al.

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2023

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“…They stated that apodizers could be optimized for the application of phase masks on these apertures and compared these results to those of E-VLT type apertures. Habib et al ( 2010 ) and Azagrouze et al ( 2010 ) introduced a new approach to interferometric apodization, called IAH technique, which utilizes homothety. This method yields results similar to those obtained with a circular aperture using step-like transmission.…”

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confidence: 99%

Interferometric apodization by homothety – II. Experimental validation

Chafi,

El Azhari,

Azagrouze

et al. 2023

Monthly Notices of the Royal Astronomical Society

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This work presents the results of experimental laboratory tests on the apodization of circular and rectangular apertures using the Interferometric Apodization by Homothety (IAH) technique. The IAH approach involves splitting the amplitude of the instrumental PSF into two equal parts. One of the two produced PSFs undergoes homothety to change its transverse dimensions while its amplitude is properly controlled. The two PSFs are then combined to produce an apodized image. The diffraction wings of the resulting PSF are subsequently reduced by some variable reduction factor, depending on an amplitude parameter γ and a spread parameter η. This apodization approach was implemented in the laboratory using an interferometric set-up based on the Mach–Zehnder Interferometer (MZI). The experimental results exhibit a strong agreement between theory and experiment. For instance, the average experimental contrast obtained at a low angular separation of 2.4λ/D does not exceed 5 × 10−4. This work also allowed us to study the influence on the apodizer’s performance of some parameters, such as the wavelength and the density of the neutral filters.

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confidence: 99%

Interferometric apodization by homothety – II. Experimental validation

Chafi,

El Azhari,

Azagrouze

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Interferometric apodization by homothety – I. Optimization of the device parameters

Chafi

Azhari

Azagrouze

et al. 2023

Monthly Notices of the Royal Astronomical Society

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This study is focused on the very high dynamic imaging field, specifically the direct observation of exoplanetary systems. The coronagraph is an essential technique for suppressing the star’s light, making it possible to detect an exoplanet with a very weak luminosity compared to its host star. Apodization improves the rejection of the coronagraph, thereby increasing its sensitivity. This work presents the apodization method by interferometry using homothety, with either a rectangular or circular aperture. We discuss the principle method, the proposed experimental setup, and present the obtained results by optimizing the free parameters of the system while concentrating the maximum of the light energy in the central diffraction lobe, with a concentration rate of 93.6% for the circular aperture and 91.5% for the rectangular geometry. The obtained results enabled scaling the various elements of the experiment in accordance with practical constraints. Simulation results are presented for both circular and rectangular apertures. We performed simulations on a hexagonal aperture, both with and without a central obstruction, as well as a segmented aperture similar to the one used in the Thirty Meter Telescope (TMT). This approach enables the attainment of a contrast of approximately 10−4 at small angular separations, specifically around 1.8λ/D. When integrated with a coronagraph, this technique exhibits great promise. These findings confirm that our proposed technique can effectively enhance the performance of a coronagraph.

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Homothetic apodization of circular aperture HACA: simulation results

Cited by 2 publications

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Interferometric apodization by homothety – II. Experimental validation

Interferometric apodization by homothety – II. Experimental validation

Interferometric apodization by homothety – I. Optimization of the device parameters

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