670 W Single-frequency Retrievable Multi-tone All-fiber MOPA

We demonstrated a single-frequency retrievable multi-tone all-fiber laser in master oscillator power-amplification (MOPA) configuration with the highest recorded power of 670 W. The seed laser runs in multi-tone regime by phase modulating a single-frequency fiber laser using a sine wave signal. Power amplification of the multi-tone master oscillator is then implemented by four cascaded all-fiber power amplifier and a power scaling up to 670 W is achieved. A proof of-concept experiment for retrieving single-frequency laser from the high power multi-tone laser is carried out by implementing a demodulation signal, which is pi phase shift of the modulation signal, on the output laser at a relative low power level. Results indicated that the single frequency laser can be retrieved with a sideband suppression of more than 20 dB at the power level of 670 W. This method may provide a feasible way for power scaling of single-frequency laser over the SBS limitation in fiber amplifier.