Kévin Barjot | Searcharxiv

arXiv2026

Stellar interferometry with a K-band integrated optics beam combiner instrument at the CHARA Array - I. First on-sky fringes for CHARIOT

We present the instrument description and the first on-sky observations for the new CHara ARray Integrated Optics Testbench (CHARIOT) at the CHARA Array. CHARIOT is a 2-telescope proof-of-concept instrument that utilises a fibre-connectorised beam combiner fabricated by ultrafast laser-inscription in Infrasil quartz glass, which presents low-OH contamination and high transparency over the whole K-band. With its fibre-connected architecture, CHARIOT is designed as a plug-and-play testbed instrument to test and validate fibred astrophotonic components on-sky. At this point, CHARIOT is able to measure raw fringe squared visibilities with a sub-1% precision for stars with K-mag<2. Under poor to moderate seeing conditions, the current limiting magnitude for fringe detection is K-mag = 5.212 (HD210824). These results demonstrate that CHARIOT's performance is already comparable to the former JouFLU instrument. With additional improvements, the limiting magnitude could be extended and the precision for fainter stars improved. The successful on-sky demonstration paves the way for a new high precision K-band beam combiner instrument at the CHARA array.

astro-ph.IM↗

arXiv2023

Caractérisation et intégration de composants d'optique intégrée sur l'interféromètre fibré FIRST au télescope Subaru pour l'étude des protoplanètes en accrétion

Protoplanets accreting matter seem to feature a strong emission at $\text{H}α$ wavelength and the contrast of the system is then weaker at these wavelengths and thus more accessible. Measuring this emission from a protoplanet allow to characterize the accretion processes hence to study the mechanisms of planetary formation. The Fibered Interferometer foR a Single Telescope (FIRST) instrument uses the concept of fibered pupil remapping in the visible, integrated on the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) telescope. Its principle is to sub-divide the entrance pupil into sub-pupils whose beams are injected into single mode optical fibers. The lattest have the double advantage of applying a spatial filtering on the wavefront thus suppressing the optical aberrations at the scale of the sub-pupils, at the same time as the remapping of the sub-pupils. FIRST has demonstrated that it can detect stellar binaries at a resolution below the diffraction limit of the telescope with this concept. The replica of a new version of this instrument (FIRSTv2) has been built in laboratory to allow the development of the integrated optics technology. My thesis work demonstrates its feasibility for HRA imaging, in order to improve the contrast performances of the instrument. The fringes of each pair-wise combination of sub-pupils are measured via a temporal sampling and their phase are estimated. Data analysis estimates the spectral differential phase, which is a self-calibrated observable of the atmospheric and instrumental perturbations. Thus, from a protoplanetary source simulator, I was able to demonstrate that FIRSTv2 could detect a protoplanetary companion at a separation equivalent to 0.7 l / B from the central source, with a contrast of about 0.5. Finally, FIRSTv2 were integrated on the SCExAO bench for its first light.

astro-ph.IM↗