Strain effects in the absorption coefficient and relative refractive index change in double asymmetric AlxGa1-xN/GaN quantum wells

We theoretically investigate the optical absorption and the relative change in the index of refraction in asymmetric double zinc-blende AlxGa1-xN/GaN quantum wells. Particular emphasis is put in revealing the influence of lattice strain on these properties. For that purpose, the electronic energy structure is determined in the framework of the effective mass and parabolic band approximations whilst the strain effects are incorporated with the use of the model solid theory. The corresponding optical coefficients are then computed through the expressions obtained within the compact matrix density formulation. Linear and nonlinear contributions are reported as functions of the widths of both the separating central potential barrier and the left-hand quantum well.