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. 2020 Aug 7;11:3975. doi: 10.1038/s41467-020-17843-9

Fig. 4. Stabilization of main soliton repetition rate by using Vernier dual-comb method.

Fig. 4

The rep-rate of the main solitons is stabilized by locking fv to a Rb-referenced oscillator, and the locking is verified by using EOM method. a Rep-rate measurement using EOM method. The locking loop is engaged at the time near 50 s. The gate time (τ) is 10 ms. b Allan deviation calculated from the unlocked and locked repetition rates that are measured with the EOM method. The locking loop has ~kHz servo bandwidth. Within the servo bandwidth, the Allan deviation goes down as 1/τ. Beyond the servo bandwidth, the Allan deviation is similar to that of the free-running unlock rep-rate. The error in the rubidium clock has been corrected for the Allan deviation of the locked rep-rate. This is done by synchronizing the EOM and the soliton rep-rate to the same rubidium reference. In the entire measurement, the repetition rate of the Vernier solitons is not stabilized, and there is no feedback control of the laser-cavity detuning for the Vernier solitons.