# Experimental test of a 40 cm-long R=100 000 spectrometer for exoplanet characterisation

## TL;DR

This paper presents a proof-of-concept for a compact, high-resolution echelle spectrometer using VIPA technology, aimed at exoplanet characterization through high-dispersion spectroscopy in the infrared.

## Contribution

It introduces an innovative VIPA-based spectrometer design with high spectral resolution, compact size, and suitability for exoplanet studies, demonstrating its potential for future astronomical instrumentation.

## Key findings

- Achieved high spectral resolution (R > 80,000) in a 40 cm footprint spectrometer.
- Demonstrated effective use of VIPA technology for high-contrast exoplanet spectroscopy.
- Presented a cooled, fiber-fed optical setup suitable for adaptive optics integration.

## Abstract

High-resolution spectroscopy is a key element for present and future astronomical instrumentation. In particular, coupled to high contrast imagers and coronagraphs, high spectral resolution enables higher contrast and has been identified as a very powerful combination to characterise exoplanets, starting from giant planets now, up to Earth-like planet eventually for the future instruments. In this context, we propose the implementation of an innovative echelle spectrometer based on the use of VIPA (Virtually Imaged Phased Array, Shirasaki 1996). The VIPA itself is a particular kind of Fabry-Perot interferometer, used as an angular disperser with much greater dispersive power than common diffraction grating. The VIPA is an efficient, small component (3 cm x 2.4 cm), that takes the very advantage of single mode injection in a versatile design. The overall instrument presented here is a proof-of-concept of a compact, high-resolution (R > 80 000) spectrometer, dedicated to the H and K bands, in the context of the project High-Dispersion Coronagrahy developed at IPAG. The optical bench has a foot-print of 40 cm x 26 cm ; it is fed by two Single-Mode Fibers (SMF), one dedicated to the companion, and one to the star and/or to a calibration channel, and is cooled down to 80 K. This communication first presents the scientific and instrumental context of the project, and the principal merit of single-mode operations in high-resolution spectrometry. After recalling the physical structure of the VIPA and its implementation in an echelle-spectrometer design, it then details the optical design of the spectrometer. In conclusion, further steps (integration, calibration, coupling with adaptive optics) and possible optimization are briefly presented. Keywords: Echelle Spectrometer, High Spectral Resolution, Exoplanets, High-Dispersion Coronography, Infrared, Adaptive Optics, SPHERE