Perturbation Method in the Analysis of thin deformed Films and the   possible Application
  The perturbation method for the analysis of thin, manifestly deformed films is given. The application of the method the excitons in the film has shown that those have the effective mass essentially depending on the propagation direction. The effects of a mechanical deformation of the film were investigated. It was concluded that the film could serve as an emiter of infrared radiation if the mechanical deformation periodically changes in time. 
Vjekoslav Sajfert