High-resolution molecular spectroscopy in micrometric thin cells

Gas cell molecular spectroscopy has far-reaching applications in frequency referencing and fundamental physics, however, most experiments up to date remain voluminous. For this reason, efforts have been recently made to perform molecular spectroscopy in miniaturized or compact platforms. Hollow core fibers filled with acetylene gases have been fabricated [1] providing frequency references for telecommunication wavelengths. Porous materials have also been proposed as platforms for molecular spectroscopy, allowing for an increased interaction length due to multiple light scattering [2] . Finally, sapphire thin cells have been filled with high-density CO 2 gas to study molecule-wall collisions [3] . In the above set-ups, the resolution remains limited due to Doppler or transient broadening, or extreme homogeneous broadening due to intermolecular collisions at high densities.