  We present a theoretical investigation of the dynamics of the dielectric
constant of noble metals following heating with ultrashort pulsed laser beams
and the influence of the temporal variation of the associated optical
properties in the thermomechanical response of the material. The effect of the
electron relaxation time on the optical properties based on the use of a
critical point model is thoroughly explored for various pulse duration values
(i.e. from 110fs to 8ps). The proposed theoretical framework correlates the
dynamical change of optical parameters, relaxation processes and induced
strains-stresses. Simulations are presented by choosing gold as a test material
and we demonstrate that the consideration of the aforementioned factors leads
to significant thermal effect changes compared to results when static
parameters are assumed. The proposed model predicts a substantially smaller
damage threshold and a large increase of the stress which firstly underlines
the significant role of the temporal variation of the optical properties and
secondly enhances its importance with respect to the precise determination of
laser specifications in material micromachining techniques.
