Nonlinear Intersubband Refractive Index Changes Research Articles

Influence of the internal heterostructure on nonlinear refractive index changes for intersubband transitions in spherical quantum dotquantum well nanoparticles

The electronic spectra and optical properties of one electron spherical quantum dot-quantum well structure consisting of a CdSe core surrounded by ZnS and CdSe shells and capped by material with a higher electron potential barrier compared with CdSe is investigated. Eigenfunctions and corresponding energies are calculated using effective mass approximation. For allowed transitions between ground and three excited states (1s, 2p, 3d, and 2s), we have calculated dipole transition matrix elements and linear and third-order nonlinear intersubband refractive index changes for different CdSe core radii and ZnS and CdSe shells thicknesses. Electron wave functions and energy of states are considerably affected by the dimensions of core and shells. The localization regime of electron in 1s, 1p, 1d, and 2s states and hence transition energies and dipole matrix elements of 1s-1p, 1p-1d, and 1p-2s transitions can be controlled by core and shell dimensions.

LINEAR AND NONLINEAR INTERSUBBAND REFRACTIVE INDEX CHANGES IN WURTZITEAlGaN/GaNDOUBLE 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.

Electric field effect on the linear and nonlinear intersubband refractive index changes in asymmetrical semiparabolic and symmetrical parabolic quantum wells

By using the displacement harmonic variant method and the compact density matrix approach, the linear and nonlinear intersubband refractive index changes (RICs) in a semiparabolic quantum well (QW) with applied electric field have been investigated in detail. The simple analytical formulae for the linear and nonlinear RICs in the system were also deduced. The symmetrical parabolic QWs with applied electric fields were taken into account for comparison. Numerical calculations on typical GaAs QWs were performed. The dependence of the linear and nonlinear RICs on the incident optical intensity, the frequencies of the confined potential of the QWs and the strength of the applied electric field were discussed. Results reveal that the RICs in the semiparabolic quantum well system sensitively depend on these factors. The calculation also shows that the semiparabolic QW is a more ideal nonlinear optical system relative to the symmetric parabolic QW systems.