Characterization of a multi-etalon array for ultra-high resolution spectroscopy

TL;DR

This paper presents a high-resolution multi-etalon array achieving a resolving power of 600,000, enhancing exoplanet atmospheric spectroscopy capabilities, especially for detecting biosignatures like oxygen with future ELTs.

Contribution

The study demonstrates a 2-FPI array prototype reaching 600,000 resolution and explores dualons as resolution boosters for current spectrographs.

Findings

Prototype achieves 600,000 resolving power.

Multi-cavity etalons can boost resolution of existing spectrographs.

Potential to improve detection of biosignatures in exoplanet atmospheres.

Abstract

The upcoming Extremely Large Telescopes (ELTs) are expected to have the collecting area required to detect potential biosignature gases in the atmosphere of rocky planets around nearby low-mass stars. Some efforts are currently focusing on searching for molecular oxygen (O2), since O2 is a known biosignature on Earth. One of the most promising methods to search for O2 is transmission spectroscopy in which high-resolution spectroscopy is combined with cross-correlation techniques. In this method, high spectral resolution is required both to resolve the exoplanet's O2 lines and to separate them from foreground telluric absorption. While current astronomical spectrographs typically achieve a spectral resolution of 100,000, recent studies show that resolutions of 300,000 -- 400,000 are optimal to detect O2 in the atmosphere of earth analogs with the ELTs. Fabry Perot Interferometer (FPI) arrays have been proposed as a relatively low-cost way to reach these resolutions. In this paper, we present performance results for our 2-FPI array lab prototype, which reaches a resolving power of 600,000. We further discuss the use of multi-cavity etalons (dualons) to be resolution boosters for existing spectrographs.