Power-efficient mode-locked thulium fiber oscillator and non-linear chirped pulse amplifier for 1789 nm ultrashort pulse generation

We report a compact, all-fiberized mode-locked thulium (Tm)-doped fiber laser operating at 1789 nm, optimized for high-efficiency, short-wavelength ultrafast pulse generation. Utilizing a double-pass pumping scheme, the mode-locked Tm-fiber oscillator achieves a low pump threshold of 110mW, enabling the use of a simple single-mode laser diode as the pump source and significantly enhancing the compactness of the oscillator. At a low pump power of 250 mW, the oscillator can generate a dissipative soliton with a pulse energy of 0.7nJ and a compressed duration of 270 fs. A simple, single-stage Tm-doped fiber amplifier, configured in a chirped pulse amplification scheme, effectively boosts the pulse energy to 41.5 nJ. Further enhancement is achieved using non-linear chirped pulse amplification, which induces coherent spectral broadening and enables pulse compression down to 180 fs. The proposed laser system combines compactness, high efficiency, and ultrafast performance, demonstrating strong potential for high-resolution, label-free three-photon microscopy in biological imaging applications.