Effect of the Carrier-Envelope-Offset Dynamics on the Stabilization of a Diode-Pumped Solid-State Frequency Comb

We investigate the dynamics of the carrier-envelope-offset (CEO) frequency, ƒ _CEO, controlled by a pump current on the self-referencing of an optical frequency comb generated from a diode-pumped solid-state laser at 1.56 μm. We observe a reversal point in the tuning of ƒ _CEO with the pump current. Between the low- and high-frequency region in the dynamic response of ƒ _CEO to pump current modulation, we observe a significant phase shift of ≈180  deg in the transfer function. As a result, it is impossible to stabilize ƒ _CEO at a pump current above the reversal point, although the free-running CEO beat at this point has a higher signal-to-noise ratio than underneath the reversal point at which the locking is straightforward. Our results indicate that a high signal-to-noise ratio and a low-noise CEO beat are not sufficient indicators for the feasibility of comb self-referencing in cases for which CEO dynamics play a dominant role.