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

Abstract

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