LINEAR AND NONLINEAR INTERSUBBAND REFRACTIVE INDEX CHANGES IN WURTZITE AlGaN/GaN DOUBLE QUANTUM WELLS: EFFECTS OF PIEZOELECTRICITY AND SPONTANEOUS POLARIZATION

Based on the density-matrix approach and iterative treatment, a detailed procedure for the calculation of the linear and nonlinear intersubband refractive index changes (RICs) in wurtzite GaN-based coupling quantum wells (CQWs) is given. The simple analytical formulas for electronic eigenstates and the linear and third-order nonlinear RICs in the systems are also deduced. Numerical result on a typical AlGaN/GaN CQW shows that the linear and nonlinear RICs sensitively depend on the structural parameters of the CQW system as well as the doped fraction of nitride semicondutor.