Two-photon absorption in crossed electric and magnetic fields

Abstract

The effect of a crossed electric (E) and a magnetic (H) field on the two-photon interband electronic transitions in semiconductors is investigated. The approach we follow treats the electric field as a small perturbation in the presence of magnetic fields of different strengths. The behaviour of the two-photon absorption coefficient depends mainly on the ratioE/H. A numerical application to the case of ZnS shows what follows: i) ForE≦103 V/cm andH≧100 kG, the behaviour is of magnetic type and gives singularities corresponding to the Landau levels (n) in the different bands. The effect of the electric field is to reduce the value of the energy gap and to destroy then selection rules. ii) AsE/H increases, the electric field decreases the separation between the Landau levels,i.e. goes to the continuum limit. iii) AsE>6·103 V/cm, the behaviour becomes of electric type for which this approach is no longer valid.