Realization of carrier envelope phase control in an erbium-doped all-fiber comb via an intracavity electrical polarization controller

We present an erbium-doped all-fiber comb that is realized via intracavity piezoelectric mechanical responses by inserting an electrical polarization controller (EPC) for carrier envelope phase offset (f_ceo) control and sticking a piezoelectric transducer (PZT) for repetition rate (f_r ) stabilization. With only three components inside the oscillator, it facilitates an all-fiber comb system with high integration and robustness. Besides f_ceo control, smart, recoverable, and precise searching of mode-locked states can also be achieved by finely tuning the EPC driving voltages. The f_ceo signal can be tightly phase-locked due to the 20 kHz 3 dB bandwidth of the EPC device. Compared with the traditional pump feedback mode, the EPC approach exhibits a larger and flatter gain in the near-zero-dispersion zone of the fiber comb, corresponding to less EPC induced intracavity fluctuations. It is also a benefit for reducing cross regulation between f_r and f_ceo in long-term stabilization of the comb.