Multicore fibre photonic lanterns for precision radial velocity Science

• Published in: Monthly notices of the Royal Astronomical Society Vol. 475; no. 3; pp. 3065 - 3075
• Main Authors: Gris-Sánchez, Itandehui, Haynes, Dionne M, Ehrlich, Katjana, Haynes, Roger, Birks, Tim A
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 01.04.2018
• Subjects: Coupling; Fibers; Lanterns; Noise; Photonics; Radial velocity; Shakers; Signal to noise ratio; Spectral resolution; Spectrographs; Stability; Stretchers; Velocity; Wavelengths; instrumentation: miscellaneous; methods: data analysis; instrumentation: spectrographs; techniques: radial velocities; techniques: image processing
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stx3278

Abstract Incomplete fibre scrambling and fibre modal noise can degrade high-precision spectroscopic applications (typically high spectral resolution and high signal to noise). For example, it can be the dominating error source for exoplanet finding spectrographs, limiting the maximum measurement precision possible with such facilities. This limitation is exacerbated in the next generation of infra-red based systems, as the number of modes supported by the fibre scales inversely with the wavelength squared and more modes typically equates to better scrambling. Substantial effort has been made by major research groups in this area to improve the fibre link performance by employing non-circular fibres, double scramblers, fibre shakers, and fibre stretchers. We present an original design of a multicore fibre (MCF) terminated with multimode photonic lantern ports. It is designed to act as a relay fibre with the coupling efficiency of a multimode fibre (MMF), modal stability similar to a single-mode fibre and low loss in a wide range of wavelengths (380 nm to 860 nm). It provides phase and amplitude scrambling to achieve a stable near field and far-field output illumination pattern despite input coupling variations, and low modal noise for increased stability for high signal-to-noise applications such as precision radial velocity (PRV) science. Preliminary results are presented for a 511-core MCF and compared with current state of the art octagonal fibre.