Polariton effects in multiple-quantum-well structures of CdTe/Cd1-xZnxTe

Strong effects of coupling between exciton and electromagnetic modes in periodic multiple-quantum wells of CdTe/Cd0.87Zn0.13Te with the period equal to either one-half or one-fourth of the light wavelength in the barrier material are experimentally demonstrated by means of reflectivity studies. The measurements are performed for various thicknesses of the cladding layer, incidence angles, magnetic fields, and degree of disorder. Reflectivity spectra as well as energies and radiative lifetimes of the polaritonlike excitations are computed for the relevant structures. It is demonstrated that current theory describes quantitatively the main features of the reflectivity. For multiple-quantum wells with the period equal to one-half of the photon wavelength in the barrier material a strong enhancement of the exciton-photon coupling is observed. This enhancement allows the detection in the frequency domain of the modification of the radiative coupling due to the presence of a dielectric mirror. A considerably different behavior of structures with the period equal to one-half and one-fourth of the light wavelength is predicted to show up in four-wave mixing time-resolved measurements. It is suggested that the description of the luminescence requires a thorough consideration of localization and thermalization dynamics.