The main utility of ultrafast (picosecond and femtosecond) pulsewidths in laser material processing applications is the ability for heat-free ablation. Heatfree, however, is not universally guaranteed for all pulsewidths and all materials. Every material has a unique single-pulse "athermal" time constant that is associated with the electron-phonon interaction time of the material and typically ranges from short picosecond to very long picosecond. Furthermore, the orders of magnitude of the time constants are generally dependent upon the material class, such as metal, semiconductor, or dielectric, so a pulsewidth that is "athermal" for one material may not be for another. Even armed with this knowledge cold ablation can still yield heat-affects when certain processing parameters allow for incubation to build up heat in the material. We present here an in depth study of the heat-affects on a variety of materials as a function of pulsewidth across the entire picosecond regime. Both single-pulse and multi-pulse incubation affects are discussed. The materials we investigate include metals such as stainless steel and aluminium, semiconductors (silicon), aluminosilicate glass, and polymers. We report both the threshold for ablation, as well as the size and quality of the heat-affected-zones as a function of pulsewidth from 2 to 500 picoseconds.
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