Compensation of loss to approach –1 effective index by gain in metal-dielectric stacks J. Zhang, H. Jiang, B. Gralak, S. Enoch, G. Tayeb and M. Lequime Eur. Phys. J. Appl. Phys., 46 3 (2009) 32603 Published online: 25 July 2008 DOI: 10.1051/epjap:2008148