Abstract
Stimulated Raman scattering (SRS) is a critical nonlinear effect that constrains the power scaling and beam quality of high-power fiber laser delivery systems. In this work, we propose and experimentally demonstrate a distributed chirped tilted fiber Bragg grating (CTFBG) array for effective SRS suppression during kilowatt-level laser delivery. Four CTFBGs were inscribed at regular intervals along a 5-meter-long 25/250 μm large-mode-area double-cladding germanium-doped fiber using femtosecond laser phase-mask technology. The CTFBG array was integrated into a master oscillator power amplifier fiber laser system for performance evaluation. Experimental results show that without the CTFBG array, the delivery system outputs 2407 W with a signal-to-Raman peak intensity difference of 43 dB. After incorporating the CTFBG array, the output power reaches 2344 W, and the signal-to-Raman intensity difference is enhanced to 50 dB, achieving a 7 dB improvement in SRS suppression. The distributed array architecture enables progressive Raman filtering along the delivery path, effectively suppressing the nonlinear accumulation of SRS during propagation. This approach provides a practical pathway for extending the power delivery capability of fiber laser systems.