Localization of Light: Dual Symmetry between Absorption and   Amplification
  We study the propagation of radiation through a disordered waveguide with a complex dielectric constant $\epsilon$, and show that dual systems, which differ only in the sign of the imaginary part of $\epsilon$, have the same localization length. Paradoxically, absorption and stimulated emission of radiation suppress the transmittance of the waveguide in the same way. 
J.C.J. Paasschens (Philips Research Laboratories), T.Sh. Misirpashaev,   and C.W.J. Beenakker (Leiden University)