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. Thi s result is used, within the effective medium approximation framework, to s tudy the dielectric function when charged cylindrical inclusions are embedd ed in a matrix of a different dielectric. The results are applied to the po rous silicon case as an example where this effect might be important. The p resence of charge produces a blue shift in the optical response. We conclud e that charge produces in porous silicon a similar behavior as quantum conf inement and may give a significant change in its optical properties. (C) 20 01 Elsevier Science Ltd. All rights reserved.