Deep‑Penetration Multilayer Femtosecond Laser Cutting of Cf/SiC Composites This study presents a femtosecond laser multilayer cutting method for Cf/SiC composites, achieving 400 µm‑wide deep grooves with a depth‑to‑width ratio exceeding 8 and minimal taper. Optimized parameters (12 µm scan spacing, 20 µm step depth) enable smooth sidewalls, controlled ablation transition (non‑thermal to thermal), and minimal material damage. The research elucidates the cutting mechanism and demonstrates high‑quality, low‑loss processing, making femtosecond multilayer cutting an ideal solution for aerospace CMC component machining.