Interface polariton modes in GaAs AlAs superlattices with randomly distributed layer thickness

We study here the dispersion relation and propagation of the interface polariton modes in specially constructed disordered GaAs/AlAs superlattices by using the transfer matrix method. The calculation of dispersion relation shows that the polariton modes exist only in two frequency regions, occur in some minibands and some isolated modes in each polariton band due to disordered effect and exhibit only small shift by varying the degree of thickness randomness, which are qualitatively in agreement with the experimental conclusions. We also find that some modes of interface polaritons with special frequencies are completely unscattered by randomness and can propagate through the structure, in contrast to the localized theory of one-dimensional (1D) disordered systems, while the other modes rapidly decay and are completely scattered. These results can be used to obtain the more realistic photonic band gaps and locations of the resonant photonic states in the 1D systems. This provides a possibility of building a high-quality optical filter. (C) 1999 American Institute of Physics. [S0021-8979(99)01711-9].