
Ultrafast Processes in Solid-State Materials 549
The dependence of the modulation amplitude on ϑ results from the electro-optic
effect, which here is responsible for the phonon-induced reflectivity change.
11.4.5. Laser-Induced Surface Disordering
In a strongly absorbing material, the energy deposited in a small surface layer
by a short light pulse can locally raise the temperature beyond the melting point.
What is the response of matter to a δ-function impulse of energy, sufficient to
cause melting? “How fast does melting occur?” is a question of fundamental
interest, which involves changes in order and structure. In addition to the possi-
bility of