Abstract
The properties of polaritons in a disordered material are studied under the Coherent Potential Approximation. The main results are as follows: (i) The concept of effective wave vector can be used to describe the polariton in a disordered material. (ii) The polariton dispersion in a disordered material is similar to that in a crystalline material. (iii) The polariton lifetime due to the disorder increases as its energy departs from the resonant region.