Watt-class 1.4 µm all-fiber optical frequency comb system based on Er-doped fiber laser and fiber Raman amplifier

Generation and power scaling of optical frequency combs at wavelengths outside the rare-earth ion gain bands, such as the 1.4 µm region, have been challenging despite the importance of this region for various applications. We developed a 1.4 µm optical frequency comb seed source with a pulse duration of 38 fs and an average output power of 44 mW by nonlinear wavelength conversion on an Er-doped mode-locked fiber laser comb with a repetition rate of 152 MHz. By amplifying this source using a lumped fiber Raman amplifier, we generated a pulsed optical frequency comb source with an average output power of 1.24 W while maintaining coherence. Additionally, the pulses were compressed using a simple grating pair compressor, resulting in a pulse duration of 818 fs.