Abstract
In the context of mid-infrared astronomical aperture synthesis, heterodyne interferometry has been identified as a potential solution to combine a large number of telescopes in the 10 µm–20 µm wavelength regime. In search of an alternative to costly and technologically difficult digital correlation, we have proposed to correlate wide bandwidth radio-frequency signals in the analog domain, using photonics components developed in the frame of telecommunication applications. In this paper, we propose an extension to amplitude modulation of our initial proposition, in which the encoding of the heterodyne signal was performed through phase modulation. Both schemes are compared, and an experimental demonstration of correlation between two signals using amplitude modulation is presented. Our experiment shows that this concept has important advantages over phase modulation, in particular with regard to the requirements on phase stabilization. The possibility to scale-up the photonics concept to the recombination of a large number of telescopes, and a large number of spectral channels to increase the instantaneous bandwidth coverage of infrared heterodyne interferometry, is discussed. This study shows that the necessary technological building blocks of a pathfinder instrument adaptable to existing astronomical facilities are available.
© 2021 Optical Society of America
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