Chapter 2 A Study of Tunable Metamaterial Devices for the THz Region N. Chikhi, E. Di Gennaro, E. Esposito, A. Andreone Abstract In order to cope with the “THz Gap”, metamaterial based devices operating at about 1 THz have been designed to have a tunable response. We studied the electromagnetic behaviour of periodic structures consisting of different “unit cells” based on the concept of Split Ring Resonator (SRR). The devices response in the required frequency region is simulated using a commercial electromagnetic code. Different modulation mechanisms have been investigated, including the use of liquid crystals, MEMS, semiconducting substrates. 2.1 Introduction During the last two decades substantial progress has been achieved in the develop- ment of THz science and technology. However, there are several restrictions which limit the full exploitation of fruitful applications covering this frequency region. One of the main constraints is the so called “THz Gap”, which is basically due to the lack of appropriate response at those frequencies for many naturally existing materials. This problem can be solved using artificially structured electromagnetic materials, named metamaterials, typically comprised of periodic arrays of sub-wavelength metallic structures within or on a dielectric or semiconducting substrate. The use of this type of material, on an appropriate form such a Split Ring Resonators (SRR), could find application for the development of novel devices operating in this fre- quency region and aimed at filtering, modulating, and switching the electromagnetic signal. Since the first extensive studies on metamaterials, the attention of most re- searchers has been focused on the linear properties of these composite structures. N. Chikhi, E. Di Gennaro, A. Andreone CNR-SPIN UOS Napoli and Department of Physics, Universit` a di Napoli Federico II, Naples, Italy, e-mail: chikhi@na.infn.it E. Esposito CNR-IC Institute of Cibernetics, Pozzuoli (Na), Italy, e-mail: e.esposito@cib.na.cnr.it M.F. Pereira and O. Shulika (eds.), Terahertz and Mid Infrared Radiation: Generation, 9 Detection and Applications, NATO Science for Peace and Security Series B: Physics and Biophysics, DOI 10.1007/978-94-007-0769-6 2, © Springer Science+Business Media B.V. 2011