As confirmed exoplanets climb into the thousands, the era of exoplanets discovery is giving way to exoplanet characterization. The most desirable scenario is one where the exoplanet can be directly imaged. Direct imaging not only delivers orbital parameters, but also yields the chemical composition of the atmosphere. The potential for habitable zone exoplanets to exhibit biosignatures in such data from a visionary future instrument drives intense interest. However, this requires to simultaneously reach extremely high star-to-planet contrast (from 10<sup>4</sup> to 10<sup>8</sup>) and extremely high angular resolution (around and below the diffraction limit). Accomplishing all this through the atmosphere blurred by turbulence remains a critical challenge, yet it is one that nulling interferometry in combination with extreme adaptive optics aims to meet. This technique overcomes the contrast problem by removing the starlight with destructive interference, permitting the faint light coming from the planet to remain. In this paper, we present the latest evolution of nulling interferometry instrumentation: the integrated- photonic nuller. It allows spatial filtering, multiple simultaneous baselines, simultaneous photometric channels and simultaneous measurement of the "nulled" signal (the light emitted from the planet after cancelling the starlight) as well as the "anti-nulled" signal (the channel containing the redirected starlight). Exploiting these fundamental optical principles, the delivery of imaging and differential spectroscopy of exoplanetary systems becomes possible. This paper describes a pathfinder that has implemented these ideas into a robust and compact photonic-chip platform known as the GLINT (Guided-Light Interferometric Nulling Technology) project.
Ultrafast laser inscription is a technique to create low-loss three dimensional optical circuits within bulk dielectrics that is compatible with a wide range of optical materials. Its unique capabilities and the ability to rapid prototype and quickly iterate through different designs has made it exceptionally attractive for astrophotonics. This paper will summarize the basic aspects of ultrafast laser inscription and review recent progress in its application to astrophotonics, such as stellar interferometry.
With many thousands of exoplanets discovered one of the important next steps in astronomy is to be able to characterise them. This presents a great challenge and calls for new observational capabilities with both high angular resolution and extreme high contrast in order to efficiently separate the bright light of a host star to that of a faint companion. Glint South is an instrument that uses photonic technology to perform nulling interferometry. The light of a star is cancelled out by means of destructive interference in a photonic chip. One of the challenges is the star light injection into the chip. This is done by a unique active system that optimises the injection and provide low order correction for the atmospheric turbulence. We are reporting on the latest progress following several tests on the Anglo Australian Telescope.