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- Gurvits, L. I., et al.
(författare)
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The science case and challenges of spaceborne sub-millimeter interferometry: the study case of TeraHertz Exploration and Zooming-in for Astrophysics (THEZA)
- 2021
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Ingår i: Proceedings of the International Astronautical Congress, IAC. - 0074-1795. ; A7
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Konferensbidrag (refereegranskat)abstract
- Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the super-massive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope (EHT) and various pioneering results of the Space VLBI mission RadioAstron provided new momentum in high angular resolution astrophysics. In both mentioned cases, the angular resolution reached the values of about 10−20 microrcseconds (0.05−0.1 nanoradian). Angular resolution is proportional to the observing wavelength and inversely proportional to the interferometer baseline length. In the case of Earth-based EHT, the highest angular resolution was achieved by combining the shortest possible wavelength of 1.3 mm with the longest possible baselines, comparable to the Earth’s diameter. For RadioAstron, operational wavelengths were in the range from 92 cm down to 1.3 cm, but the baselines were as long as ∼350,000 km. However, these two highlights of radio astronomy, EHT and RadioAstron do not”saturate” the interest to further increase in angular resolution. Quite opposite: the science case for further increase in angular resolution of astrophysical studies becomes even stronger. A natural and, in fact, the only possible way of moving forward is to enhance mm/sub-mm VLBI by extending baselines to extraterrestrial dimensions, i.e. creating a mm/sub-mm Space VLBI system. The inevitable move toward space-borne mm/sub-mm VLBI is a subject of several concept studies. In this presentation we will focus on one of them called TeraHertz Exploration and Zooming-in for Astrophysics (THEZA), prepared in response to the ESA’s call for its next major science program Voyage 2050 (Gurvits et al. 2021). The THEZA rationale is focused at the physics of spacetime in the vicinity of super-massive black holes as the leading science drive. However, it will also open up a sizable new range of hitherto unreachable parameters of observational radio astrophysics and create a multi-disciplinary scientific facility and offer a high degree of synergy with prospective “single dish” space-borne sub-mm astronomy (e.g., Wiedner et al. 2021) and infrared interferometry (e.g., Linz et al. 2021). As an amalgam of several major trends of modern observational astrophysics, THEZA aims at facilitating a breakthrough in high-resolution high image quality astronomical studies.
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- Ravishankar, Ajith Padyana, et al.
(författare)
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Fabrication of self-organized InP nanopillars by ion-bombardment for optoelectronic applications
- 2019
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Ingår i: 2019 IEEE 14th Nanotechnology Materials and Devices Conference, NMDC 2019. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728126371
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Konferensbidrag (refereegranskat)abstract
- In this work, we investigate a wafer-scale, lithography-free, self-assembled indium phosphide (InP) nanopillars fabrication method based on ion bombardment. The influence of process conditions, such as the substrate temperature, ion beam energy, ion beam incidence angle, and processing time, were investigated with regard to the geometry (shape, diameter and height) and density of the fabricated nanopillars. For optimized process conditions, we show that by controlling the ion beam incidence angle (while rotating the sample), the shape (tapered to cylindrical) and average diameter (~75-150 nm) can be tuned and where InP nanopillar heights of ~600 nm were realized. It is shown that by modifying the shapes of the InP nanopillars, broadband anti-reflection can be obtained with average reflectance as low as ~4% in the wavelength range of 400-900 nm.
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