2016
DOI: 10.1051/0004-6361/201628739
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Optimizing the subwavelength grating ofL-band annular groove phase masks for high coronagraphic performance

Abstract: Context. The annular groove phase mask (AGPM) is one possible implementation of the vector vortex coronagraph, where the helical phase ramp is produced by a concentric subwavelength grating. For several years, we have been manufacturing AGPMs by etching gratings into synthetic diamond substrates using inductively coupled plasma etching. Aims. We aim to design, fabricate, optimize, and evaluate new L-band AGPMs that reach the highest possible coronagraphic performance, for applications in current and forthcomin… Show more

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Cited by 31 publications
(34 citation statements)
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“…Depending on the initial result it is possible to adjust the process parameters to reach a sidewall angle which gives the widest region of acceptable performances [6] for varying w and d. The variation in angle gives freedom for both w and d. The line width can both decrease or increase depending on the amount of residual resist layer left after the lithography step and on the anisotropy of the aluminum etch process as it can etch underneath the mask pattern. However, the diamond etching preserves the line width of the grating as long as the mask is sufficiently thick [7]. The line width is therefore set to about 50% of Λ in the electron beam printed master pattern as it still can produce a good component while the the line width is between 40 and 60% of Λ.…”
Section: Designmentioning
confidence: 99%
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“…Depending on the initial result it is possible to adjust the process parameters to reach a sidewall angle which gives the widest region of acceptable performances [6] for varying w and d. The variation in angle gives freedom for both w and d. The line width can both decrease or increase depending on the amount of residual resist layer left after the lithography step and on the anisotropy of the aluminum etch process as it can etch underneath the mask pattern. However, the diamond etching preserves the line width of the grating as long as the mask is sufficiently thick [7]. The line width is therefore set to about 50% of Λ in the electron beam printed master pattern as it still can produce a good component while the the line width is between 40 and 60% of Λ.…”
Section: Designmentioning
confidence: 99%
“…The substrates were circular with a diameter of 10 mm and thickness of 300 μm. For each produced component, two substrates were prepared in parallel: one of them leading to a functional coronagraphic element, while the second one (twin) was cracked for cross-sectional characterization, as there is no method yet for measuring the grating parameters without breaking the component [7]. Cleaning and pattern transfer steps as well as the aluminum and silicon etching are described in detail in [6], the main difference is in the lithography technique known as Solvent Assisted Microcontact Molding (SAMIM).…”
Section: Manufacturingmentioning
confidence: 99%
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“…The upgrades aim to enable unique exoplanet science. NIRC2 was upgraded with an L-band vortex coronagraph, [1][2][3][4][5] now offered in shared-risk mode. The NIRC2 L-band vortex enabled the discovery of new protoplanet candidates, 6, 7 disks, 8 and allowed us to constraint mass accretion rates in protoplanetary disks with gaps.…”
Section: Introductionmentioning
confidence: 99%