Femtosecond pulse amplification at 1770 nm using thulium- and terbium-doped fluoride fibers

We present a chirped pulse amplification system for ultrashort 1770 nm pulses, utilizing a multistage fiber amplifier based on thulium-doped core and terbium-doped cladding fluoride fibers. The seed pulse is generated through stimulated Raman scattering in a silica fiber, pumped by an erbium-doped fiber laser. After temporal stretching with a silica dispersion compensation fiber, the pulse undergoes amplification in a two-stage Tm:Tb:ZBLAN amplifier. The pulse can be further amplified with a power amplifier based on a thulium-doped fluoride fiber. The system achieves an average power of ~1 W at megahertz repetition rates. Using a grism compressor, the pulse is efficiently compressed down to 254 fs.