Microscopic energy transport through photon-electron-phonon interactions during ultrashort laser ablation of wide bandgap materials. Part I: Photon absorption

The new phenomena induced by femtosecond lasers lead to the new area of ultrafast science. It is a significant challenge to explain the phenomena associated with complex non-equilibrium and non-linear processes. Although there is a growing body of experimental observation, a comprehensive model remains undeveloped. We review the challenges in understanding the photon absorption stage mainly for the femtosecond ablation of wide bandgap materials at the intensities of 10¹³-10¹⁴ W/cm². Major opinions and challenges in ionization mechanisms are presented by primarily considering multiphoton ionization and avalanche ionization.