Terahertz electromagnetic (EM) radiation is in the far-infrared
light band. f = 1 THz in frequency is 299.79 l.lm in wavelength, 47.99 K in temperature,
and 4.14 meV in energy. It is well-known that in semiconductor nanostructures
such as two-dimensional electron gases (2DEGs), the conducting electrons are
confined within nanometer distances so that the electron kinetic energy, electronic
subband energy, Fermi energy, plasmon energy, phonon energy, etc. are of t.he order
of the THz photon energies. This implies that the intense THz radiation can couple
strongly to the 2DEG systems. In these device systems, the rate for electronic scattering
with impurities arid phonons can also be comparable with the
THz photon frequencies, which suggests that the intense THz radiation can modify
strongly the processes for momentum and energy relaxation of elect.rons in a 2DEG.
Furthermore, for semiconductor materials such as GaAs, f = 1 THz in frequency
is 2.38 T in magnetic field. This indicates that in the presence of an inteuse THz
laser field and a quantising magnetic field, interesting radiation phenomena can be
observed ill the 2DEG systems. Hence, intense THz laser radiation is a powerful t.ool
in the investigation of semiconductor nanostrtlctures such as 2DEGs.