High-power all-fiber femtosecond fiber laser system at 2μm

In this work, we report a high power all-fiber femtosecond pulse thulium-doped fiber laser (TDFL) at 2 μm. The master oscillator is mode-locked by the SESAM and is centralized in 1945.2 nm at 23.96 MHz, running in a stable soliton mode-locking state. The amplifier is a monolithic master oscillator power amplifier (MOPA) configuration and the maximum average laser power is measured to be 6.44 W. Due to the strong nonlinear effect of the low repetition frequency pulse in the amplification process, we can achieve pulse width compression directly in an all-fiber configuration and compress the pulse width to sub-200-fs at 6.44 W. In addition, we investigated the evolution of the spectrum and autocorrelation traces during pulse amplification in different pre-chirp conditions by adding different lengths of PM2000D positive dispersion fibers between the oscillator and the amplification stage. Thanks to the good performance of the final output, such as the high power femtosecond pulse and reliable power stability, this TDFL is anticipated to be an excellent choice for practical and scientific applications or be further amplified for higher power femtosecond pulse laser.