Nanoexplosion initiated by short-wavelength radiation: Optical breakdown in soft matter revisited

The term “laser microexplosion” has been introduced to stress the violent character of the optical breakdown by laser radiation under conditions of tight focusing. Generally, the starting phase of the breakdown has been neglected by the assumption of absorption triggered by the presence of damage precursors. The application of the plasticity–elasticity theory in the analysis of the dynamics of this phenomenon has not been extensively examined to date. This paper formulates a phenomenological model attempting to explain the creation of nanovoids in a soft matter under irradiation by a flux of extreme ultraviolet (XUV)/soft x-ray photons. The combined action of plastic deformation and dissociation waves on soft matter is found to be responsible for the material modifications. It is suggested that localized ( volume ≃ λ 3) abundance of energy, coming most likely from photon bunching, constitutes the real onset of the photo-ablative decomposition. It is shown that the coincidental presence of some small number of energy carriers (2–3 XUV photons in the considered case) in such a small volume triggers processes denoted from now on as a laser nanoexplosion. The effect is considered to be the first step in the optical breakdown followed by an intense material removal resembling, to some extent, a phase explosion.