Three years of harvest with the vector vortex coronagraph in the thermal infrared

Abstract

For several years, we have been developing vortex phase masks based on sub-wavelength gratings, known as Annular Groove Phase Masks. Etched onto diamond substrates, these AGPMs are currently designed to be used in the thermal infrared (ranging from 3 to 13 µm). Our AGPMs were first installed on VLT/NACO and VLT/VISIR in 2012, followed by LBT/LMIRCam in 2013 and Keck/NIRC2 in 2015. In this paper, we review the development, commissioning, on-sky performance, and early scientific results of these new coronagraphic modes and report on the lessons learned. We conclude with perspectives for future developments and applications.

Near-infrared pyramid wavefront sensor for Keck adaptive optics: opto-mechanical design

“…The choice to develop a near-infrared PWS was driven by the high performance of visible PWS, the recent availability of near-infrared e-APD arrays, and measured performance improvements using a near-infrared tip-tilt sensor with the Keck I laser guide star (LGS) AO system. [1][2][3] The near-infrared PWS will be a key component of the Keck Planet Imager and Characterizer (KPIC) project. The characterizer part of KPIC includes a fiber injection unit (FIU) that will feed exoplanet light to the NIRSPEC spectrograph.…”

Commissioning and first light results of an L'-band vortex coronagraph with the Keck II adaptive optics NIRC2 science instrument

“…15. Regarding the results achieved with the vortex at the NIRC2 on the Keck II telescope as of today, the most representative data has been acquired on October 24th 2015 on the benchmark target 12,13 HR8799.…”

High-charge and multiple-star vortex coronagraphy from stacked vector vortex phase masks

“…Importantly, the pro posed approach does not require the development of higher order or inhomogeneous vortex phase masks. The practical consequence is that state of the art second order vortex phase masks already at work in large telescopes [6] could be combined to create and test high charge vortex coronagraphs. This implies the realization of HWPs having similar throughput and retardance performances which, however, does not represent a technological challenge.…”

“…Future giant telescopes will require the management of pointing noise/errors, lower order aberrations, and finite spatial extension of the source, which implies the development of higher order vortex masks. Their realization is especially difficult for subwavelength gratings [6,11], while liquid crystal polymers allow easier fabrication of a vector vortex phase mask of the order higher than two [12].…”

“…Vortex coronagraphs have been found to be promising enough to foster long term design and manufac turing efforts to produce a helical phase mask of the second order (l 2). Depending on the considered spectral range, a few technologies have been developed, e.g., (1) subwavelength gra tings [3] today at work in several ground based large telescopes [6], (2) liquid crystal polymer masks [7] that have also been implemented on a few instruments [8,9], and (3) photonic crys tals [10]. Future giant telescopes will require the management of pointing noise/errors, lower order aberrations, and finite spatial extension of the source, which implies the development of higher order vortex masks.…”