Negative Refraction in Extraordinary Transmission Metamaterial confirmed by a wedge experiment M. Navarro-Cía 1 , M. Beruete 1 , I. Campillo 2 , F. Falcone 1 and M. Sorolla 1 1 Millimeter Wave Laboratory, Universidad Pública de Navarra, Campus Arrosadía s/n, 31006- Pamplona, Spain. Phone: +34 948 169324, Fax: +34 948 169720 miguel.navarro@unavarra.es , miguel.beruete@unavarra.es , francisco.falcone@unavarra.es , mario@unavarra.es 2 CIC nanoGUNE Consolider, Paseo Mikeletegi 56, 301, 20009 Donostia, Spain i.campillo@nanogune.eu Abstract Extensive research efforts are being put forth in order to achieve a low-loss Left-Handed Metamaterial (LHM) [1] at optical frequencies, where losses are a big concern. The approach to solve this problem by the Millimeter Wave Laboratory at the Public University of Navarre is to design a LHM exhibiting Extraordinary Optical Transmission (EOT) [2], which could alleviate the losses problem. Indirect phase techniques were used to claim left-handed propagation characteristic of a Metamaterial made by just stacking several perforated plates showing Extraordinary Transmission at millimeter waves [3]. However, it has been recently shown a pure geometrical and experimental demonstration of a low-loss negative refraction structure [4] in the millimeter wave band by using a metamaterial prism made by just stacking sub-wavelength metallic hole arrays sandwiched in air, see Fig. 1(a). The prototype is made of several stacked sub-wavelength hole array perforated in an aluminum plate with: hole diameter a = 2.5 mm, transversal periodicities, d x = 3 mm and d y = 5 mm, and metal thickness w = 0.5 mm. Here, Extraordinary Transmission occurs near 57 GHz contrasting with the fact that an individual hole begins to propagate at 70 GHz. The longitudinal period between the hole array plates is d z = 1.5 mm. To obtain the prism structure, it is necessary to remove step by step the number of periods along the x dimension, see Fig. 1(a). The angular evolution of the received radiated power has been measured by using an AB Millimetre TM Quasioptical Vector Network Analyzer at different distances from the prism structure. Moreover, it can be inferred the index of refraction of the structure from these measurements. This work presents new results on the evolution of the co-polar and cross-polar measurements, which confirm the theoretical previsions, see Fig. 1(b). (a) (b) Fig.1. (a) Photograph of the prototype. (b) Polar representation of the radiated power for two different frequencies within the left- handed band at 400 mm from the prism.