Optical properties of charged inclusions

We consider a point charge embedded in an infinite dielectric cylinder and calculate its dielectric function dependent on the charge distribution. This result is used, within the effective medium approximation framework, to study the dielectric function when charged cylindrical inclusions are embedded in a matrix of a different dielectric. The results are applied to the porous silicon case as an example where this effect might be important. The presence of charge produces a blue shift in the optical response. We conclude that charge produces in porous silicon a similar behavior as quantum confinement and may give a significant change in its optical properties.