Fabrication tolerant chalcogenide mid-infrared multimode interference coupler design with application for Bracewell nulling interferometry

Abstract

Understanding exoplanet formation and finding potentially habitable exoplanets is vital to an enhanced understanding of the universe. The use of nulling interferometry to strongly attenuate the central starlight provides the opportunity to see objects closer to the star than ever before. Given that exoplanets are usually warm, the 4 microns Mid-Infrared region is advantageous for such observations. The key performance parameters for a nulling interferometer are the extinction ratio it can attain and how well that is maintained across the operational bandwidth. Both parameters depend on the design and fabrication accuracy of the subcomponents and their wavelength dependence. Via detailed simulation it is shown in this paper that a planar chalcogenide photonic chip, consisting of three highly fabrication tolerant multimode interference couplers, can exceed an extinction ratio of 60 dB in double nulling operation and up to 40 dB for a single nulling operation across a wavelength window of 3.9 to 4.2 microns. This provides a beam combiner with sufficient performance, in theory, to image exoplanets.

Assigned issue as Vol. 23 No. 3 in Op. Express

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Cited by in corpus (7)

• The path towards high-contrast imaging with the VLTI: the Hi-5 project
• Kernel-nulling for a robust direct interferometric detection of extrasolar planets
• Astrophotonics: astronomy and modern optics
• Large Interferometer For Exoplanets (LIFE): IV. Ideal kernel-nulling array architectures for a space-based mid-infrared nulling interferometer
• Large Interferometer For Exoplanets (LIFE): VII. Practical implementation of a five-telescope kernel-nulling beam combiner with a discussion on instrumental uncertainties and redundancy benefits
• Tri-coupler geometries for achromatic nulling interferometry in the near-infrared
• Photonic mid-infrared nulling for exoplanet detection on a planar chalcogenide platform