Multi-Heterodyne Differential Phase Measurement of Microcombs

Microcombs have been an intense area of research in frequency synthesis and metrology over the past decade. The measurement of amplitude and phase of microcombs provides unique insight into the nonlinear cavity dynamics. Different techniques have been reported to this aim, including iterative pulse shaping [1], dual-comb interferometry [2] and lately stepped-laser interferometry [3], resulting in unprecedented sensitivity and bandwidth. Here, we report a dramatic simplification of the latter setup by using another microcomb instead of a stepped tunable laser. This results into the acquisition of complex spectra in a single-scan without requiring additional optical components and high-end detection units.