Exciton--polaritons in ternary mixed crystals

In this paper the bulk exciton polaritons in ternary mixed crystals (TMCs) are investigated in the Born--Huang approximation. The numerical results of the polariton frequencies as functions of the wave-vector and the compositions for ternary mixed crystals Al_xGa_1 - xAs, Cd_xZn_1 - xSe, and Al_xGa_1 - xN are obtained and discussed. The new dispersion characteristics for exciton--polaritons in TMC systems are found in comparison with binary crystals. The splitting of the two branches of exciton--polariton frequencies varies nonlinearly with the composition of TMCs and has a minimum in the long-wavelength range.