Subgigahertz-resolution table-top spectrograph calibrated with a 4-GHz optical frequency comb

We developed a table-top multipass spectrograph with a 610-MHz resolution (corresponding to a resolving power of 450,000) and a throughput of 10%. The spectrograph was calibrated with a 4-GHz optical frequency comb (OFC) that did not require filtering cavities, which would hinder long-term operation. The OFC is centered at a wavelength of 1  μm, which makes it suitable for the investigation of M dwarf stars and the compact size of the OFC-calibrated spectrograph makes it suitable for use in small to mid-scale observatories.