Sixth order segmented vector vortex phase masks and shaped pupils for future telescopes

Jun Nishikawa; Naoshi Murakami; Yosuke Tanaka; Hiromi Muramatsu; Kenta Yoneta; Mizuki Asano

doi:10.1117/12.3018226

18 July 2024 Sixth order segmented vector vortex phase masks and shaped pupils for future telescopes

Jun Nishikawa, Naoshi Murakami, Yosuke Tanaka, Hiromi Muramatsu, Kenta Yoneta, Mizuki Asano

Author Affiliations +

Proceedings Volume 13096, Ground-based and Airborne Instrumentation for Astronomy X; 130969J (2024) https://doi.org/10.1117/12.3018226
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Conference Poster

Abstract

High-contrast coronagraphs have been developed to detect and characterize exo-planets with contrasts of 10^-8~10^-10. One method used for coronagraphs is the vector vortex phase mask, and a 6th-order one is required to sufficiently suppress the light from stars with finite apparent diameters using future large telescopes at the ground and in space. We manufactured 12- and 24-segmented sixth-order vector vortex phase masks with photonic crystal waveplates, and their fast axis orientations are 90 degrees and 45 degrees in adjacent regions, respectively. A three-layer structure was designed to cover a broad band of 600-1000nm. The design contrast for the phase mask alone is 8e-6, and we expect to achieve the final contrast by polarization filtering. We found that the retardation of the phase mask was almost coincident to the design curve. As for the 24-segment phase mask, a shaped pupil was designed as a combined element to exhibit the performance of the phase mask in the pupil shape of the TMT, which has the obstructions of the secondary mirror, the spiders, and the segment boundaries. The shaped pupil design has a transmittance of about 70% and a contrast of 10^-7 within the outer working angle of 10 lambda/D. A shaped pupil was manufactured by chromium etching on a quartz substrate, and we observed the reduction of the diffracted light within 8 lambda/D.

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Jun Nishikawa, Naoshi Murakami, Yosuke Tanaka, Hiromi Muramatsu, Kenta Yoneta, and Mizuki Asano "Sixth order segmented vector vortex phase masks and shaped pupils for future telescopes", Proc. SPIE 13096, Ground-based and Airborne Instrumentation for Astronomy X, 130969J (18 July 2024); https://doi.org/10.1117/12.3018226

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