  We reveal that due to the presence of disorder oscillations of the order
parameter amplitude called the Higgs mode can be effectively excited by the
external electromagnetic radiation in usual BCS superconductors. This mechanism
works for superconductors with both isotropic s-wave and anisotropic, such as
d-wave, pairings. The non-linear response in the presence of impurities is
captured by the quasiclassical formalism. We demonstrate that analytical
solutions of the Eilenberger equation with impurity collision integral and
external field drive coincide with the exact summation of ladder impurity
diagrams. Using the developed formalism we show that resonant third-harmonic
signal observed in recent experiments is naturally explained by the excitation
of Higgs mode mediated by impurity scattering.
