The quantum transport equation for electrons under intense
radiation was solved. The frequency-dependent electrical current
driven directly by the radiation field is obtained. The electrical
field of the laser radiation is included exactly and the
electron-impurity interaction is included up to the second order.
Our formalism rests on the solution of density matrix for
successive order of photon processes. It is found that as
radiation intensity increases, the rate of multiphoton absorption
and emission can exceed that of single photon processes. In the
strong electron-photon coupling limit, rate of emission is
comparable to that of absorption.
Chao Zhang, Chao Zhang,
"Nonlinear electrical transport in quantum wells under intense radiation", Proc. SPIE 5646, Nonlinear Optical Phenomena and Applications, (28 January 2005); doi: 10.1117/12.572434; https://doi.org/10.1117/12.572434