| Popis: |
Much can be learned about charge and magnetization dynamics at surfaces and in nanometer thickness films through terahertz emission spectroscopy (TES). In some respects, TES is the difference-frequency analog of second harmonic generation (SHG). As such, interface-specific properties contribute to the generation of a THz pulse upon ultrafast optical excitation. In addition, there can be bulk contributions as well, as is also true in SHG. The dependence of THz pulse emission on surface orientation has been used to study carrier dynamics, both real and virtual, in GaAs(111). We find that the dependence on the angle of linearly polarized excitation is well described by known theory. Magnetization dynamics in polycrystalline nickel films ranging in thickness from 5 nm to 60 nm have also been characterized with TES. Distinct bulk and surface contributions each play a role, and their origins are discussed. |
