The second-harmonic generation due to the intersubband transitions in nonparabolic two-level quantum well systems is discussed theoretically taking into account the depolarization effect.
The influence of permanent dipole moments of quantized states on intersubband second harmonic generation based on quantum-interference induced transparency in semiconductor quantum wells is explored using the harmonic balance method. The permanent moments are found to be quite important: they affect the transparency condition, especially at larger pump intensities. Hence, both the conversion efficiency and the optimal interaction path length change significantly when accounting for the permanent moments, and the conversion efficiency is reduced.
We obtain pulse-driven Rabi oscillations guided by a generalization of the rotating-wave approximation to include, in the optical-Bloch equations, two-level systems with a time-varying transition energy. We achieve this by using chirped pulses with the central frequency given by the time-varying transition energy. Using this approach, we predict Rabi oscillations in intersubband transitions in a two-subband n-type modulation-doped quantum well by taking into account the time-dependent intersubband energy-gap renormalization due to depolarization-shift effects. We obtain Rabi oscillations for jpi (j=0,1,2, ) pulses in the presence of dephasing.
The effect of the depolarization field on the doubly resonant frequency mixing due to resonant intersubband transitions in asymmetric quantum wells, with only the ground subband occupied, is discussed. Calculations are performed in the framework of the perturbative density matrix formulation with relaxation time approximation. The results show that in the considered system the depolarization effect can be included by simple replacement (in the one-electron expression for the nonlinear susceptibility) of the intersubband energy by the depolarization shifted intersubband energy.