Fig. 4
From: Silicon-chip-based mid-infrared dual-comb spectroscopy
Repetition rate tuning of the dual-comb source. The frequency spacing of the dual-comb source is dictated by the spacing of each of the modelocked combs. The plot shows 14 MHz spacing (a) and a 26 MHz spacing (b). The spacing is tuned by adjusting the thermoelectric coolers to change the resonance position of the microresonators
