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Proceedings Paper

New technologies for nulling interferometry: laboratory demonstration of integrated optics beam combiners in the L and M bands (Conference Presentation)
Author(s): Lucas Labadie; Stefano Minardi; Jan Tepper; Romina Diener; Robert R. Thomson; Jorg-Üwe Pott; Stefan Nolte

Paper Abstract

In the era of large telescopes and RV/Transit planetary missions, nulling interferometry remains a competitive technique for the characterization of Earths and Super-earths around Sun analogs in the mid-IR (Léger 2015, ApJ 808, 194). This is a spectral range where a number of bio-signatures can be accessed from space. One challenge of nulling is to benefit from well-established and qualified infrared fibers and integrated optics capable of mitigating the instrumental constraints on the beam combination and wavefront filtering to reach high extinction ratios. Such photonics devices have reached high maturity in the near-IR range as in the case of the integrated optics (IO) beam combiner of GRAVITY at the VLTI, leading to unprecedented interferometric accuracy. Driven by the need of next-generation interferometers, we expand the photonic approach towards longer wavelengths and develop IO combiners based on the ultrafast laser writing technique. We developed single-mode, low-loss evanescent couplers in gallium lanthanum sulfide with a 50/50 splitting behavior around 3.4 µm and characterized the intrinsic chromaticity by FTS. High monochromatic and broadband contrasts are measured with unpolarized light at 3.39µm (>98%), over the L band (>95%), and over the M Band (4.5-4.8µm) (>95%). Our analysis of the interferometric visibilities and phase shows a small differential birefringence in the component and negligible differential dispersion. This results points out the promising properties of mid-infrared laser writing integrated optics devices to serve as high quality beam combiners. The extension to a four-aperture architecture appears plausible, with care to be taken about the impact of the design on the total throughput.

Paper Details

Date Published: 19 September 2017
Proc. SPIE 10400, Techniques and Instrumentation for Detection of Exoplanets VIII, 104001H (19 September 2017); doi: 10.1117/12.2273414
Show Author Affiliations
Lucas Labadie, Univ. zu Köln (Germany)
Stefano Minardi, Friedrich-Schiller-Univ. Jena (Germany)
Jan Tepper, Univ. zu Köln (Germany)
Romina Diener, Friedrich-Schiller-Univ. Jena (Germany)
Robert R. Thomson, Heriot-Watt Univ. (United Kingdom)
Jorg-Üwe Pott, Max-Planck-Institut für Astronomie (Germany)
Stefan Nolte, Friedrich-Schiller-Univ. Jena (Germany)

Published in SPIE Proceedings Vol. 10400:
Techniques and Instrumentation for Detection of Exoplanets VIII
Stuart Shaklan, Editor(s)

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