Magnetic field effect on the third harmonic generation in quantum well wires with triangular cross-section

The conduction subband structure of a triangular cross-section GaAs/AlGaAs quantum well wire under magnetic field is theoretically investigated by taking into account a finite confining potential and two orientations of the field relative to the wire axis. The calculation of the subband energy levels is based on a two-dimensional finite element method within the effective mass approximation. It is shown that the magnetic field could be used for tuning the intersubband transitions: in the transverse field there is an obvious augment of the energy levels, whereas an axial field induces blueshifts/redshifts on the subband energies, depending on the azimuthal quantum number. We found that an axial orientation of the field allows the third harmonic generation and this process is enhanced for a particular polarization of the incident light and a proper field strength. A third-order nonlinear susceptibility with a peak value of 10−13(m/V)2 is predicted when the triple resonance condition is achieved.