Development of an erbium-fiber-laser-based optical frequency comb at NTSC

We report the research progress of an erbium-fiber-based optical frequency comb with repetition rate 232 MHz. Its repetition rate is stabilized to a continuous wave laser via an intra-cavity electro-optic modulator and a piezo-transducer, yielding an in-loop frequency instability about 2.1×10⁻¹⁶ @ 1s. The carrier envelope offset (CEO) frequency with a signal-to-noise ratio of 45 dB for 300 kHz resolution spectrum is detected by using a common path f−2f interferometer. CEO frequency is locked to a RF reference frequency by controlling the pump current. The frequency instability induced by in-loop CEO frequency is about 2.9×10⁻¹⁶@ 1s. The frequency count in use is a Π-type counter from K&K.