Polar Mixing Optical Phonon Spectra in Wurtzite GaN Cylindrical Quantum Dots： Quantum Size and Dielectric Effects

The interface-optical-propagating （IO-PR） mixing phonon modes of a quasi-zero-dimensional （QOD） wurtzite cylindrical quantum dot （QD） structure are derived and studied by employing the macroscopic dielectric continuum model. The analytical phonon states of IO-PR mixing modes are given. It is found that there are two types of IO-PR mixing phonon modes, i.e. p-IO//z-PR mixing modes and the z-IO//p-PR mixing modes existing in QOD wurtzite QDs. And each IO-PR mixing modes also have symmetrical and antisymmetrieal forms. Via a standard procedure of field quantization, the Frohlich Hamiltonians of electron-（IO-PR） mixing phonons interaction are obtained. Numerical calculations on a wurtzite GaN cylindrical QD are performed. The results reveal that both the radial-direction size and the axial-direction size as well as the dielectric matrix have great influence on the dispersive frequencies of the IO-PR mixing phonon modes. The limiting features of dispersive curves of these phonon modes are discussed in depth. The phonon modes ＂reducing＂ behavior of wurtzite quantum confined systems has been observed obviously in the structures. Moreover, the degenerating behaviors of the IO-PR mixing phonon modes in wurtzite QOD QDs to the IO modes and PR modes in wurtzite Q2D QW and QID QWR systems are analyzed deeply from both of the viewpoints of physics and mathematics.     

Resonant reflectance dips induced by coupled surface plasmon polaritons in thin metal-film/dielectric superlattices

The optical reflectance of metal films changes dramatically as the film thickness becomes thinner than the electron mean free path. We have developed a transfermatrix formalism for deducing the dispersion relations of the electromagnetic waves in infinite and semi-infinite metal-dielectric superlattices by taking into account the presence of the size effect and coupled plasmon waves. This work shows that the resonance frequency occurring at the reflecting dip increases while the bandwidth decreases as the thickness of the dielectric films increases. Reducing the values of p and q shifts the resonance frequency upward and yields multiple numbers of minimum reflectivity.