Astrophotonic Absorption Correlation Spectroscopy using Silicon Microring Resonators

The absorption spectra of distant targets can be used for remote gas detection. However, the detection of very faint absorption features is difficult since noise can dominate the molecular signal in the acquired spectrum. Rather than using typical dispersive spectroscopy, high sensitivity remote gas sensing is possible by correlation spectroscopy using a spectral matching filter. In this work, we use a thermo-optically tunable nanophotonic silicon waveguide ring resonator as an integrated spectral filter to obtain a correlation signal proportional to the absorption spectrum of a specific gas. We demonstrate the ability to resolve very small absorption depth changes using integrated photonics at the level required for the characterization of exoplanet atmospheres during transits of their host stars.