Abstract
The dependence of the second harmonic susceptibility on the quantum well width and the composition of the Al y Ga 1-y As quantum well was theoretically investigated. Subband envelope wave functions and eigenenergies were calculated self-consistently by simultaneously solving the Schrodinger equation and the Poisson equation. The Schrodinger equation was solved by the transfer matrix method and the Poisson equation by numerical integration. The energy-dependent effective mass due to energy-band nonparabolicity was also considered. This analysis was then used to determine the energy-band nonparabolicity induced lowering of the subband eigenenergy. Based on the theoretical calculation, the compositionally asymmetric coupled quantum well (CACQW) gave a very strong nonlinear optical effect. Second harmonic susceptibility as high as 220 nm/V can be achieved for the CACQW structure. Variation of the second harmonic susceptibility under the applied electric field showed a very interesting phenomenon of the electric field quenching effect.