Purcell effect in wire metamaterials
  We study theoretically the enhancement of spontaneous emission in wire metamaterials. We analyze the dependence of the Purcell factor dependence on wire dielectric constant for both electric and magnetic dipole sources, and find an optimal value of the dielectric constant for maximizing the Purcell factor for the electric dipole. We obtain analytical expressions for the Purcell factor and also provide estimates for the Purcell factor in realistic structures operating in both microwave and optical spectral range. 
Alexander N. Poddubny, Pavel A. Belov, and Yuri S. Kivshar
physics.optics cond-mat.mes-hall cond-mat.mtrl-sci