An RIZ-Band Astrocomb with Versatile Offset Control

Laser frequency combs (LFCs) offer ideal calibration lines for astronomical spectrographs, enabling extreme precision radial velocity (RV) measurements down to 10 cm s⁻¹ [1]. Inhomogeneities in the spectrograph camera, which are not fully mapped by a static field of astrocomb modes, introduce errors into the instrument point spread function (PSF), which in turn translate into RV errors. One approach to mitigating this issue is to leverage the narrow LFC lines for mapping the complete detector PSF [2], [3]. This can be achieved by an astrocomb with a tunable mode offset, allowing the comb modes to be swept across all the detector pixels [4]. In this work, we present an offset-tunable astrocomb in the RIZ band, featuring a compact Fabry-Pérot (FP) design, and offering hands-free tunability and robust filtering.