Actively mode-locked diode laser with a mode spacing stability of ∼6 × 10-14

We have studied mode spacing stability in an actively mode-locked external-cavity semiconductor laser. It has been shown that, in the case of mode spacing pulling to the frequency of a highly stable external microwave signal produced by a hydrogen standard (stability of 4 × 10-14 over an averaging period τ = 10 s), this configuration ensures a mode spacing stability of 5.92 × 10-14 (τ = 10 s).