Terahertz Science and Technology, ISSN 1941-7411 Vol. 6, No. 1, March 2013 40 Invited Paper Terahertz metamaterial absorbers Mohammad Parvinnezhad Hokmabadi, David S. Wilbert, Patrick Kung , Seongsin M. Kim * Electrical and Computer Engineering Department, University of Alabama, USA * Email: seongsin@eng.ua.edu (Received January 2, 2013) Abstract: Terahertz (THz) electromagnetic waves share a few of the characteristics of optical and gigahertz waves, which makes them suitable for a number of interesting and new applications in imaging, spectroscopy, characterization, sensing and monitoring. Recently, there has been a huge interest in developing THz devices that can achieve this potential. One of these devices is a metamaterial THz perfect absorber, which was first proposed in 2008 and is believed to form the basis for future room temperature THz detectors. Since then, a large amount of research has been focused on developing such THz absorbers with various properties, including dual band, multiband, wide band and polarization insensitivity. In this article, we present a brief review of the current state-of-the-art of THz metamaterial absorbers and discuss in more detail two specific THz absorber structures. Keywords: Terahertz, Metamaterial, Absorber doi: 10.11906/TST.040-058.2013.03.03 1. Introduction Terahertz (THz) electromagnetic (EM) waves, with a frequency ranging from 0.1 THz up to 10 THz, share a common properties with optical and gigahertz EM waves. In the infrared, optical and ultraviolet spectral range, the photon is the principal particle and fundamental concept that governs interactions between materials and EM waves, whereas at gigahertz frequencies major electron oscillations in the material are best amenable to describe material-EM wave interactions. Like micro- and millimeter waves, THz radiation can penetrate through a wide variety of non-conducting materials such as fabric, paper, plastic and wood. THz radiation is also non-ionizing and can be absorbed by molecules such as water and DNA. Moreover, since biological molecules exhibit a number of intermolecular and intramolecular modes with resonance frequencies in the THz regime, THz waves are expected to be able to interact with and reveal them with a certain degree of specificity [1]. These characteristics of THz waves make them suitable for a growing number of potential applications in biomedical imaging [2], environmental monitoring of earth [3], remote sensing of explosives [4], and semiconductor spectroscopic characterization [5, 6]. A conventional microwave absorber, called Salisbury screen, was invented in 1952 and consisted of a resistive sheet and a metallic back plane separated by a dielectric spacer [7]. Its operational principle was based on achieving impedance matching with free space through