Interface phonon–polaritons in quantum well systems of polar ternary mixed crystals

The interface phonon–polaritons in quantum well systems consisting of polar ternary mixed crystals are investigated. The numerical results of the interface phonon–polariton frequencies in the GaAs/Al_xGa_1-xAs, ZnS_xSe_1-x/ZnS, and Zn_xCd_1-xSe/ ZnSe quantum well systems are obtained and discussed. It is shown that there are six branches of interface phonon–polariton modes distributed in three bulk phonon–polariton forbidden bands in the systems. The electric fields of interface phonon–polaritons are also presented and show the interface locality of the modes. The effects of the 'two-mode' and 'one-mode' behaviours of the ternary mixed crystals on the interface phonon–polariton modes are shown in the dispersion curves.