Harmonic generation upon mixing an s-polarised wave and a wave heating a metal

It is shown that when an s-polarised wave is mixed with a wave of the same frequency, which is incident along the normal to the metal surface, three frequency-doubled waves are generated. Two of them are p-polarised and one is s-polarised. The effect of the electron and lattice temperature evolution on the SHG efficiency is described quantitatively. An anomalously strong change in the generation efficiency of an s-polarised harmonic is found during temperature variations, which leads to a noticeable change in the electron collision frequency.