Linear and nonlinear optical properties of a superlattice with periodically increased well width under electric and magnetic fields

摘要

In this paper, we have studied the electronic and optical properties of GaAs/Al_xGa_(1-x)As super-lattice with periodically increased well width. Under effective mass approximation, the finite element method is used to obtain wavefunctions and corresponding energy eigenvalues for several electric field (F) and magnetic field (B) values. We have shown that the increasing well width has a major effect on the localization of the first two energy states. The direction of the applied electric field shifts the localization position of the probability density of electrons to the left and right. For B = 0 (according to the parameters used), F = 5 kV/cm (especially for the difference between the first two energy levels (E_(12))) is a critical value. While the E_(12) value decreases in the range from -30 kV/cm to 5 kV/cm, it increases for the 5 ＜ F ＜ 30 kV/cm range. This behavior causes a red or blue shift in the optical spectrum. Also, F = -30 kV/cm causes more change in the structure than F = 30 kV/cm. In addition, the localization of the electrons is observed in the center of the superlattice under applied magnetic fields. The optical absorption coefficients and the refractive index changes are affected by applied F and B intensities. We can say that the electro-optical features of the superlattice have changed significantly with the combined effect of F and B values. This is desired for semiconductor optical device applications to have stable performances.