RSAA Colloquia / Seminars / Feast-of-Facts: Friday, 05 April 2019, 14:00-14:30; CSO Common Room

Harry-Dean Goldsmith

"Fabricating a nulling interferometer for exoplanet direction"

How do star systems form? How do planets form? What are planets made of? Can they support life? These are open questions in astronomy. To find answers we turn to exoplanet detection, specifically direct imaging methods, and the mid infrared region with its ability to penetrate dust clouds and provide molecular fingerprinting information. Direct imaging, methods that use the light from the exoplanet, has successfully imaged a number of exoplanets. A key problem in direct imaging tis the very dim light from the planet compared to the very bright light from the host star. The most widely adopted means of overcoming this is physically blocking the star with an opaque disc or a phase plate, so called coronagraphy, such observations however inherently favouring the detection of large exoplanets at a great distance form their host star. Nulling interferometry uses the light from the star itself, from multiple telescopes, to form an interferometric null over the star whilst leaving orbiting material, like gas or planets, detectable. Measuring the light in the infrared spectrum also further improves the contrast between the star and exoplanet due to the “warm” emission from forming exoplanets in particular. This project explores the use of photonic chips in nulling interferometry as a replacement for bulk optical benches. Photonics has an inherently stability and compactness advantage over bulk optics equivalent systems. This is especially relevant for future space missions. We report novel designs of a nulling interferometer, in chalcogenide glass that is transparent in the infrared up to a wavelength of 10 microns, to create a >40 dB extinction of star light over a 400 nm bandwidth.