High power noise-like pulse at 2 μm and its applications in mid-IR Raman light and flat supercontinuum

Abstract

Herein, a high-power noise-like (NL) pulse fiber laser system in the 2 μm region and its applications in mid-IR Raman stokes light and flat supercontinuum (SC) were experimentally demonstrated. An all-PM fiber configuration oscillator was constructed as the seed source which can deliver stable NL mode-locked pulse trains centered at ∼1950 nm wavelength with ∼5.37 MHz repetition rate. The pulse envelope and coherence spike widths of the NL pulse can be tunable from ∼2.5 ns to ∼3.4 ns and ∼397 fs to ∼375 fs, respectively. Relying on the magnified NL pulse, the cascaded Raman shifted stokes lights centered at ∼2148 nm and ∼2359 nm were separately achieved. Meanwhile, a flat SC with a 10 dB bandwidth of ∼480 nm (from ∼1940 nm to ∼2420 nm) was obtained after boosting in a large-mode-area fiber amplifier stage, and the average output power of ∼72 W represents the highest output power of the NL pulse in the 2 μm region, to the best of our knowledge. Moreover, we noted that the NL pulse-based spectrum broadening is much more effective than that the picosecond pulse-based. Our experimental results strongly imply that the NL pulse can be severed as an ideal laser source for the application of mid-IR spectroscopy.