Since the 1990s over 3000 planets orbiting distinct stars – known as exoplanets – have been detected. Most have used indirect techniques to determine their size and composition, key details in understanding planetary formation and the prevalence of life in the universe.

Despite recent large-scale detections of exo-planets, indirect methods fail to provide a complete picture of the planetary nursery and we must turn to alternative, albeit more difficult, methods such as directly imaging to study the planets. Specifically at mid-infrared wavelengths we are able to penetrate dust clouds that cocoon forming planets, and provide molecular information.

While direct-imaging methods have successfully imaged a number of exoplanets, a key challenge is one of contrast, the faint light from the planet compared to the dominating light from the host star. The most widely adopted means of overcoming this is by physically blocking the star with an opaque disc or a phase plate, called coronagraphy. Such observations however introduce a detection bias by inherently favouring the detection of large exoplanets at a great distance form their host star, leaving the innermost planets obscured.

Nulling interferometry uses the light from the star itself 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 thermal emission from forming exoplanets.

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, fabrication, and characterization, 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