Millisecond laser processing of sapphire assisted by femtosecond laser-induced air filament

• The fs-ms combined pulse laser (CPL) enhances sapphire ablation efficiency by 28 times compared to fs laser alone, achieving 1.73×10^7 μm³/J. • Ablation efficiency increases with ms peak power and duty ratio, but excessive thermal stress causes fragmentation beyond critical thresholds. • In-situ high-speed imaging reveals a four-stage ablation process: defect-creating, melting and ablation, spattering, and fragmentation within 1.5 ms. • The CPL method offers a promising approach for efficient laser damage of transparent, hard, and brittle materials, addressing the challenge of low optical absorption.