Eur. Phys. J. B 41, 61-65 (2004)
https://doi.org/10.1140/epjb/e2004-00294-6

Kramers-Kronig relations and sum rules of negative refractive index media

¹ Department of Physics, University of Joensuu, P.O. Box 111, 80101 Joensuu, Finland
² Department of Electrical Engineering, Lappeenranta University of Technology, P.O. Box 20, 53851 Lappeenranta, Finland

Corresponding authors: ^a kai.peiponen@joensuu.fi - ^b jarkko.saarinen@joensuu.fi

Received: 13 February 2004
Revised: 13 May 2004
Published online: 30 September 2004

Abstract

Negative refractive index media have become a hot topic in physics due to their proposed revolutionary properties, which would have drastic consequences in design of novel optical devices. We show that Kramers-Kronig relations connecting the real and imaginary parts of the complex refractive index of absorbing media are valid even though the real refractive index may take negative value at some spectral range. In addition universal sum rules for linear optical constants of negative index media are also valid. This means that negative refractive index media are not fundamentally different from regular media. Hence, any spectrum measured from negative refractive index media can be analyzed using dispersion relations and sum rules, which have so far provided information on the optical properties of materials.