Diffraction-limited integral-field spectroscopy for extreme adaptive optics systems with the Multi-Core fiber-fed Integral-Field Unit

TL;DR

This paper presents a compact, diffraction-limited integral-field spectrograph using photonic technology, enabling high-resolution exoplanet atmospheric studies with existing and future adaptive optics systems.

Contribution

It introduces a novel fiber-fed integral-field unit with photonic reformatting, demonstrating its viability for high-resolution exoplanet spectroscopy on existing telescopes.

Findings

Achieved on-sky resolving power of 2500-3000.

Successfully integrated into a 4.2m telescope for exoplanet observation.

Proved the feasibility of single-mode integral-field spectroscopy for exoplanet characterization.

Abstract

Direct imaging instruments have the spatial resolution to resolve exoplanets from their host star. This enables direct characterization of the exoplanets atmosphere, but most direct imaging instruments do not have spectrographs with high enough resolving power for detailed atmospheric characterization. We investigate the use of a single-mode diffraction-limited integral-field unit that is compact and easy to integrate into current and future direct imaging instruments for exoplanet characterization. This achieved by making use of recent progress in photonic manufacturing to create a single-mode fiber-fed image reformatter. The fiber-link is created with 3D printed lenses on top of a single-mode multi-core fiber that feeds an ultrafast laser inscribed photonic chip that reformats the fiber into a pseudo-slit. We then couple it to a first-order spectrograph with a triple stacked volume phase holographic grating for a high efficiency over a large bandwidth. The prototype system has had a successful first-light observing run at the 4.2 meter William Herschel Telescope. The measured on-sky resolving power is between 2500 and 3000, depending on the wavelength. With our observations we show that single-mode integral-field spectroscopy is a viable option for current and future exoplanet imaging instruments.