Directly imaging Earth-like exoplanets around Sun-like stars with the future Habitable Worlds Observatory (HWO) will require coronagraphic focal plane masks able to suppress starlight to the 1 × 10\u207b¹\u2070 contrast levels. Furthermore, to collect enough photons for broadband imaging and detection and to minimize the number of parallel channels for spectroscopic characterization, this level of contrast must be achieved across a 20% bandwidth. Scalar vortex coronagraphs show promise as a polarization-independent alternative to polarizationsensitive vector vortex coronagraphs, but still face chromatic limitations. New scalar vortex mask designs incorporate radial phase dimples to improve the broadband performance. We present initial manufacturing results of prototype masks of these designs including phase metrology and microscope images, in preparation for broadband chromatic characterization and starlight suppression measurements, to be taken on a high contrast imaging testbed. We also present a preliminary narrowband (2%) dark hole result achieving 1.8 × 10\u207b\u2078 average contrast from 3.5-100/D on the High Contrast Spectroscopy Testbed at Caltech. This work aims to advance the technological maturity of scalar vortex coronagraphs as a viable option for consideration for HWO.
", "doi": "10.1117/12.3020702", "publisher": "SPIE", "place_of_publication": "Bellingham, WA", "publication": "Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave", "publication_date": "2024-08-23", "pages": "1309221" }, { "id": "authors:ez8s6-r9906", "collection": "authors", "collection_id": "ez8s6-r9906", "cite_using_url": "https://authors.library.caltech.edu/records/ez8s6-r9906", "type": "conference_item", "title": "High-contrast spectroscopy testbed (HCST): tip/tilt sensing in reflection of the vector vortex coronagraph (VVC)", "author": [ { "family_name": "Bertrou-Cantou", "given_name": "Arielle", "clpid": "Bertrou-Cantou-Arielle" }, { "family_name": "Redmond", "given_name": "Susan F.", "orcid": "0000-0002-9618-4371", "clpid": "Redmond-Susan-F" }, { "family_name": "Mawet", "given_name": "Dimitri", "orcid": "0000-0002-8895-4735", "clpid": "Mawet-D" }, { "family_name": "Sercel", "given_name": "Greg P.", "clpid": "Sercel-Greg-P" }, { "family_name": "Echeverri", "given_name": "Daniel", "orcid": "0000-0002-1583-2040", "clpid": "Echeverri-D" }, { "family_name": "Desai", "given_name": "Niyati", "orcid": "0000-0002-2843-8325", "clpid": "Desai-Niyati" }, { "family_name": "Llop-Sayson", "given_name": "Jorge", "orcid": "0000-0002-3414-784X", "clpid": "Llop-Sayson-Jorge" }, { "family_name": "Ruane", "given_name": "Garreth", "orcid": "0000-0003-4769-1665", "clpid": "Ruane-G-J" }, { "family_name": "Serabyn", "given_name": "Eugene", "orcid": "0009-0009-2491-0694", "clpid": "Serabyn-Eugene" }, { "family_name": "Wallace", "given_name": "James Kent", "orcid": "0000-0001-5299-6899", "clpid": "Wallace-J-Kent" } ], "editor": [ { "family_name": "Coyle", "given_name": "Laura E." }, { "family_name": "Perrin", "given_name": "Marshall D." }, { "family_name": "Matsuura", "given_name": "Shuji" } ], "abstract": "With the identified objective of enabling Earth-like exoplanets direct detection, and characterization of their atmospheric content, the Astro2020 report has placed the maturation of exoplanet imaging technology as a key priority for the coming decade. The High Contrast Spectroscopy Testbed (HCST) within the Caltech Exoplanet Technology laboratory serves as an in-air coronagraphic testbed demonstrator, integrating a high order deformable mirror for wavefront control and a vector vortex coronagraph (VVC). HCST has demonstrated excellent in-air contrast performance, achieving 1 × 10\u207b\u2078 raw contrast in broadband light, for both the apodized off-axis segmented pupil configuration and using single mode fiber planet injection. By introducing a low-order wavefront sensor (WFS) that utilizes either the in-band or out-of-band reflected light from the VVC coupled with a tip/tilt mirror, our objective is to address dynamic errors, thereby enhancing the wavefront stability of the experiment. We present in this proceeding the first steps towards a full tip/tilt control loop, starting with the optical design of our low-order camera. We performed a drift test overnight as a diagnostic of the coronagraphic performance stability and to possibly identify causes for the drift. Conclusions show that HCST demonstrate a remarkably stable environment to perform high-contrast imaging experiments, at the level of 1 × 10\u207b\u2078 contrast.
", "doi": "10.1117/12.3019237", "isbn": "9781510675070", "publisher": "SPIE", "place_of_publication": "Bellingham, WA", "publication": "Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave", "publication_date": "2024-08-23", "pages": "130926B" } ]