Self-referenced Er-fiber laser comb with 300 MHz comb spacing

A self-referenced, passively mode-locked Er-fiber laser via nonlinear polarization rotation with fundamental repetition rate of 300 MHz is demonstrated. The stabilized repetition frequency has an out-of-loop tracking instability of 2.7times10^-13 at 1 s. The stabilized carrier-envelope offset frequency has a residual fluctuation of 1.7 mHz measured with a 1-s gate time. This is, to our knowledge, the highest repetition rate of self-referenced fiber laser comb.