Chalcogenide glass planar MIR couplers for future chip based Bracewell interferometers

TL;DR

This paper demonstrates the development and testing of chalcogenide glass planar couplers for mid-infrared interferometry, enabling compact, stable, and efficient astronomical observations beyond 3 micrometers.

Contribution

It introduces the first fabricated chalcogenide glass couplers operating at 4000 nm for interferometric nulling in exoplanet observation.

Findings

Successful theoretical and experimental performance at 4000 nm

First demonstration of mid-infrared chalcogenide couplers

Potential for advanced astronomical instrumentation

Abstract

Photonic integrated circuits are established as the technique of choice for a number of astronomical processing functions due to their compactness, high level of integration, low losses, and stability. Temperature control, mechanical vibration and acoustic noise become controllable for such a device enabling much more complex processing than can realistically be considered with bulk optics. To date the benefits have mainly been at wavelengths around 1550 nm but in the important Mid-Infrared region, standard photonic chips absorb light strongly. Chalcogenide glasses are well known for their transparency to beyond 10000 nm, and the first results from coupler devices intended for use in an interferometric nuller for exoplanetary observation in the Mid-Infrared L band (3800-4200 nm) are presented here showing that suitable performance can be obtained both theoretically and experimentally for the first fabricated devices operating at 4000 nm.