Comparative study of the ablation of materials by femtosecond and pico- or nanosecond laser pulses

A series of studies was carried out on the ablation of steel, Si₃N₄ ceramic, and diamond in air by femtosecond (200 and 900 fs) pulses of different wavelengths (532 and 266 nm) and in a wide energy density range (1 — 10³ J cm^-2 ). The ablation rates were measured for different geometries of the irradiation surface [a shallow crater and a channel with a high (up to 10) aspect ratio]. The ablation rates (in a shallow crater) and the morphologies of the irradiated surface were compared for femtosecond and longer (220 ps, 7 ns) pulses. The role of the laser-generated plasma in the ablation of materials by subpicosecond pulses as well as the prospects for the practical application of ultrashort laser pulses in the processing of materials are analysed.