First on-sky demonstration of an integrated-photonic nulling-interferometer: The GLINT instrument

TL;DR

The paper reports the first on-sky demonstration of an integrated-photonic nulling interferometer, GLINT, which effectively suppresses starlight to enable precise measurements of stellar diameters, advancing exoplanet characterization techniques.

Contribution

This work introduces and demonstrates a novel integrated photonic nulling interferometer on sky, showcasing its capability for high-precision stellar measurements.

Findings

Achieved null-depth precision of ~10^{-4} on sky.

Successfully measured stellar angular diameters to milli-arcsecond accuracy.

Demonstrated the feasibility of integrated photonic interferometry for exoplanet science.

Abstract

The characterisation of exoplanets is critical to understanding planet diversity and formation, their atmospheric composition and the potential for life. This endeavour is greatly enhanced when light from the planet can be spatially separated from that of the host star. One potential method is nulling interferometry, where the contaminating starlight is removed via destructive interference. The GLINT instrument is a photonic nulling interferometer with novel capabilities that has now been demonstrated in on-sky testing. The instrument fragments the telescope pupil into sub-apertures that are injected into waveguides within a single-mode photonic chip. Here, all requisite beam splitting, routing and recombination is performed using integrated photonic components. We describe the design, construction and laboratory testing of our GLINT pathfinder instrument. We then demonstrate the efficacy of this method on sky at the Subaru Telescope, achieving a null-depth precision on sky of $\sim10^{-4}$ and successfully determining the angular diameter of stars (via their null-depth measurements) to milli-arcsecond accuracy. A statistical method for analysing such data is described, along with an outline of the next steps required to deploy this technique for cutting-edge science.