Materials that can bend light in the opposite direction to normal ('left-handed' materials) reverse the way in which refraction usually works — this negative refractive index is due to simultaneously negative permeability and permittivity^{1, 2, 3}. Here we demonstrate negative refraction of electromagnetic waves in a two-dimensional dielectric photonic crystal that has a periodically modulated positive permittivity and a permeability of unity^{4, 5, 6}. This experimental verification of negative refraction is a step towards the realization of a 'superlens' that will be able to focus features smaller than the wavelength of light.

1. Department of Physics, Bilkent University, Bilkent, 06533 Ankara, Turkey
2. Ames Laboratory, US Department of Energy, and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
3. Research Center of Crete and Department of Materials Science and Technology, University of Crete, Heraklion, 71100 Crete, Greece

Correspondence to: Ertugrul Cubukcu¹ e-mail: Email: cubukcu@fen.bilkent.edu.tr