Polaritons In Superlattices Research Articles

Plasmon-excitonic polaritons in superlattices

A theory for propagation of polaritons in superlattices with resonant plasmon-exciton coupling is presented. A periodical superlattice consists of a finite number of cells with closely located a quantum well and a monolayer of metal nanoparticles. Under study is the spectrum of hybrid modes formed of the quasitwo- dimensional excitons of quantum wells and the dipole plasmons of metal particles. The problem of electrodynamics is solved by the method of Green’s functions with taking account of the resonant polarization of quantum wells and nanoparticles in a self-consistent approximation. The effective polarizability of spheroidal particles occupying a square lattice is calculated with taking into consideration the local-field effect of dipole plasmons of the layer and their images caused by the excitonic polarization of nearest quantum well. Optical reflection spectra of superlattices with GaAs/AlGaAs quantum wells and silver particles are numerically analyzed. Special attention is paid to the superradiant regime originated in the Bragg diffraction of polaritons in superlattice. Superradiance is investigated separately for plasmons and excitons, and then for hybrid plasmonexcitonic polaritons. It is demonstrated that the broad spectrum of reflectance associated with plasmons depends on the number of cells in superlattice, and it has a narrow spectral dip in the range of plasmon-excitonic Rabi splitting.

Localized interface phonon polaritons in superlattice with a structural defect consisting of ternary mixed crystal

Abstract Using a transfer matrix method, we investigate the existence and characteristics of the localized interface phonon-polariton modes (IPPMs) in superlattice (SL) with a structural defect consisting of ternary mixed crystal (Al x Ga 1− x As). The results show that the introduction of two-mode behavior of the ternary mixed crystal leads to the rich and varied localized IPPMs spectra with new features. The characteristics and positions of the localized IPPMs in the Reststrahlen region are strongly dependent on the concentration x of the ternary mixed crystal. Moreover, it is found that the localized IPPMs are sensitive to the thicknesses of the defect and constituent layers as well as to the transverse wavenumber q ∥ .

Dispersion of Surface Polaritons in Superlattices and Their Interaction With Active Waves

Dispersion of Surface Polaritons in Superlattices and Their Interaction With Active Waves

Polaritons in superlattices and in microcavities

A description of polariton effects on excitons in multiple quantum wells (MQWs), superlattices (SLs), and semiconductor microvavities is presented. The non-local semi-classical theory in a transfer matrix formulation is adopted. The radiative width in MQWs atk=0 increases first with the number of wellsN, then goes to zero asN→∞, where stationary SL polaritons are recovered. The crossover from weak- to strong-coupling regimes for QW excitons in microcavities is described. The complex energies of the mixed exciton-radiation modes are shown to be measurable by time-resolved transmission experiments.

The influence of capping layers on surface phonon polaritons in superlattices

The influence of capping layers on surface phonon polaritons in two-layer superlattices is investigated here theoretically. General analytical expressions are given. A few illustrative applications are presented afterwards, for p-polarized non-retarded polaritons within GaAs-InAs superlattices with or without an InP capping layer. A few dispersion curves for such polaritons are drawn. The variation of the frequencies of these polaritons with the thickness of the capping layer is given.

Comment on "Continuum theories of optical phonons and polaritons in superlattices: A brief critique"

The so-called hydrodynamic (HD) model on optical-phonon modes in superlattices is critically examined. Contrary to the HD model, a comparison between TM polaritons and the Fuchs-Kliewer-type interface modes has shown that the Fuchs-Kliewer interface modes do possess Fr\ohlich potentials.

Comment on "Continuum theories of optical phonons and polaritons in superlattices: A brief critique"

We show that the zero electric displacement for longitudinal-optical-phonon modes, which leads to the proposal of hydrodynamic boundary conditions made by Ridley and Babiker [Phys. Rev. B 43, 9096 (1991)], is valid only when bulk electric fields are considered. When proper electric fields are used, which takes into account the existence of interfaces, there is no need for hydrodynamic boundary conditions.