Dielectric and Ohmic losses in perfectly absorbing metamaterials P.V. Tuong a,b , J.W. Park a , V.D. Lam b , W.H. Jang c , S.A. Nikitov d , Y.P. Lee a,n a Department of Physics, Quantum Photonic Science Research Center and RINS, Hanyang University, Seoul 133-791, South Korea b Institute of Material Sciences, Vietnamese Academy of Science and Technology, Hanoi, Vietnam c Electromagnetic Wave Institute, Korea Radio Promotion Association, Seoul, South Korea d Institute of Radioengineering and Electronics, Russia Academy of Sciences, Moscow, Russia article info Article history: Received 21 September 2012 Received in revised form 24 December 2012 Accepted 11 January 2013 Available online 31 January 2013 Keywords: Perfect absorption Metamaterials Sub-wavelength structure abstract We investigated two mechanisms of the heat generation to enhance the absorption peak of metamaterials (MMs) at the normal incidence of electromagnetic radiation. The metal–dielectric– metal sandwich-type model, in which an array of copper squares at the front and a copper plane at the back were separated by a dielectric layer, was studied for GHz frequencies. Firstly, we studied the effect of the thickness of copper square to obtain the absorption peak. The obtained results showed that absorption can be enhanced to be nearly 100% at 16 GHz by increasing the sheet resistance of the copper square. In this case, the Ohmic-loss perfect-absorption (PA) MM was devised. The PA effect was also achieved by using the loss-tangent of dielectric layer as a dissipation factor. For this purpose, we studied complex the dielectric constant of dielectric layer. The PA peak was demonstrated at the same frequency. In the second case, the dielectric-loss turns out to be dominant. The comparison between TE and TM polarizations for the PA peaks was also elucidated. & 2013 Elsevier B.V. All rights reserved. 1. Introduction Artificial materials, so-called metamaterials (MMs), have demonstrated extraordinary electrodynamic properties such as negativities of effective permittivity [1] and permeability [2] leading to negative refractive index [3,4], and applicable effects such as super-lenses [5], electromagnetic (EM) wave cloaking [6], sub-wavelength wireless power transfer [7,8] and perfect absor- ber (PA) [9–11]. They have attained great interest over past decade. In the MMs, the effective macroscopic behaviors by using small inhomogeneities are yielded by exploited the plasmonic resonances from interacting with external fields of exciting EM wave. Modulating the structural designs in ‘‘meta-atoms’’ or ‘‘meta-molecules’’ to manipulate the effective parameters is the popular strategy to result in the desired phenomena. This also creates the variety in MMs. Thanking its advantage, the MM’s effects have been not only appeared in many geometries of the inducing resonator such as rings [2,3], bars [10,11], crosses [4], flowers [12], and so on, but also presented in most of the frequency range of EM wave, from radio [13], micro [12], mm [10,11], THz [14], mid-IR [15], near-IR [16] to optical wave [17]. Black bodies, the ‘‘bodies’’ with high absorption properties, are of much importance at present in many fields of science and technol- ogy. It was firstly realized by Landy et al. [11] in 2008 under the concept of sub-wavelength artificial materials. The perfect absorp- tion of EM wave, which mean that no radiation passes through it and none is reflected, also comes to be an attractive issue in the field of MMs [9–11]. Exploiting the unnatural properties of MMs, the PA MMs have been gradually developed for promising advanced applications. For examples, PAs can be potentially used for bolometers [18], thermal images [19], efficiently capturing solar energy [20], sensor devices [21], and camouflage. In order to exploit the perfect absorption for the devices, it is important to study the heat generation to enhance the absorption peak of MMs. The mechanism of PA MMs could be understood, based on the effective material parameters. In this case, the complex parameters are functions of frequency of exciting EM wave: effective relative permittivity, eðoÞ¼ e 0 ðoÞþ e 00 ðoÞ, and effective relative permeability, mðoÞ¼ m 0 ðoÞþ m 00 ðoÞ: At the reso- nance frequency, the real parts of relative permittivity and/or permeability are adjusted to achieve of impedance matching with free space [22] by customizing the component parameters and the material. Simultaneously, the imaginary parts, e 00 ðoÞ and m 00 ðoÞ, are also manipulated to developed high dissipation factor inside the MM medium. In other words, the surface plasmas are formed in the sub-wavelength structure to reveal the PA peaks and the heat generations [23]. The impedance matching condition is obtained by utilizing the plasmonic resonance of coupling between the metallic parts in a unit cell. At the resonant frequency, the total energy of source wave provides the metallic plasma and for good optical materials they are transferred or reflected. Hence, the material should be chosen and designed Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/optcom Optics Communications 0030-4018/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.optcom.2013.01.031 n Corresponding author. Tel.: þ82 2 2281 5572; fax: þ82 2 2281 5573. E-mail address: yplee@hanyang.ac.kr (Y.P. Lee). Optics Communications 295 (2013) 17–20