Control of intersubband transitions in multiple quantum well systems

• Intersubband transitions in a multiple quantum well are studied in the presence of dc–ac fields.
• Band structure is obtained by using the finite difference method.
• Dynamics of system can be perfectly optimized by the selection of field parameters.

The dynamics of intersubband transitions in a multiple quantum well system consisting of GaAs coupled quantum wells separated by an AlxGa1−xAsAlxGa1−xAs barrier is studied in the presence of a combined static and a dynamic laser field. The eigenenergies and eigenfunctions of the system under the effect of static field are solved by a time independent Schrödinger equation using a Finite Difference method. Calculations included the effect of the intensity of static field, effect of the number of wells on various intersubband transitions, the energies and wavefunctions of the levels involved. We initiated the study with the periodic structure consisting of a few quantum wells (N=2) and studied the bound–bound and bound–continuum transitions in the mini bands formed in the wells. We have analyzed how the features characteristic of long periodic systems are formed as the number of quantum well increases. These are then used to formulate the laser–multiple quantum well interaction using a time dependent Schrödinger equation which is solved with the help of an efficient fourth order Runge Kutta method.