Generation and Compression of Self-Similar Pulses in Thulium-Doped Fiber Lasers

This study experimentally demonstrates the generation of a 2 μm self-similar pulse (SSP) in a thulium-doped fiber laser (TDFL) equipped with a nonlinear amplifying loop mirror. Self-compression in a thulium-doped fiber amplifier produced high-quality de-chirped pulses with a near Fourier-transformlimit duration of approximately 260 fs, showcasing exceptional linear compression capabilities. Additionally, spectral broadening through self-phase modulation in normal dispersion fibers yielded nonlinearly compressed pulses with a duration, singlepulse energy, and peak power of approximately 117 fs, 11.7 nJ, and 100 kW, respectively. To the best of our knowledge, this study is the first to achieve SSP mode-locked operation in an allfiber TDFL and to demonstrate excellent SSP compressibility at the 2 μm wavelength.