Generation of 160  fs pulses from core-offset nonlinear multimodal interference integrated in a 1.5 µm all-fiber laser chirped pulse amplification configuration

The high-power all-fiber femtosecond laser system demonstrated in this work operates at 1.5 µm. It uses core-offset nonlinear multimodal interference (NMI) as a saturable absorber (SA) that is integrated into a chirped-pulse amplification (CPA) configuration. The oscillator integrates an NMI-based SA that initiates mode-locking, which is then stretched and amplified to generate high-power, mode-locked pulses across all fiber-based configurations. The optimized CPA architecture operates at 1561 nm, with a 160 fs pulse width and a 13.9 MHz repetition rate, delivering a maximum average output power of 1.16 W. This configuration achieves a high peak power of 27.11 kW and a pulse energy of 4.34 nJ.