
90
Laser-Induced Damage in Optical Materials
e photoionization rate given by the Keldysh formula (Equation 4.10) exhibits
special features as a function of laser irradiance and wavelength (Figure 4.6): specic
singularities (referred to as the Keldysh singularities), gradual unlimited increase with
irradiance, and step-wise decrease with wavelength. ey can be interpreted in terms
of laser-driven Bloch oscillations of electrons (Gruzdev 2004, 2007). at interpreta-
tion also explains the transition from multiphoton to tunneling ionization and predicts
domain of laser and material parameters that provide good accuracy of evaluation of
photoioni ...