2- $\mu$ m Repetition-Rate Tunable (1–6 GHz) Picosecond Source

We have for the first time experimentally demonstrated a high repetition-rate picosecond fiber laser source at 2 μm by a spectrally masked phase modulation technique, where a phase modulator driven by a sinusoidal RF signal and a fiber Bragg grating are used to convert the output of a 2-μm continuous-wave single-longitudinal-mode diode to a picosecond pulse train. The repetition-rate of this laser source can be continuously and flexibly tuned from 1 to 6 GHz by simply changing the RF signal. We achieved a shortest pulse width of ~60 ps and a high SNR of >75 dB at an operating frequency of 6 GHz. The simplicity and robustness of such a picosecond laser as well as the ability to synchronize with an external trigger make it a highly useful source for 2-μm high speed optical data processing, communications, and metrology.