  We present theory of the carrier-optical interaction in 1D systems based on
the non-equilibrium Greens function formalism in the 4x4 k.p model. As a
representative parameters we chose the GaAs. Although theory is presented in
4x4 k.p many subbands, results and discussion section is based on the
simplified model such as 2x2 k.p model (two transverse modes). Even though 2x2
k.p model is simple enough it shows many phenomena that have not been seen
before. We focus mainly on the ballistic extraction of photogenerated free
carriers at the radiative limit which is described by the self-energy term
derived in dipole approximation and solved in self-consistent manner with
Keldysh quantum kinetic equations. Any relaxation or non-radiative
recombination mechanisms as well as excitonic features are neglected. Effect of
non-locality of electron-photon self energy term is considered and discussed.
Spontaneous emission is also considered and shown to be small in short devices
under medium bias conditions. Electron and hole spatial current oscillations
are seen and discussed. It is shown that neglecting off-diagonal correlation in
the band index not only produces quantitatively wrong results but it also
alters the qualitative picture. All simulations are done in the full-rank
approximation, with all spatial and band correlation effects are kept intact.
This allows us to study not only quantitative effects but also qualitative
behaviour.
