We demonstrate some metamaterials in the terahertz frequency regime fabricated on n-GaAs substrate. The artificially structured electromagnetic materials, which called metamaterials, has led to the realization of phenomena which cannot be obtained with natural materials. We have found many fundamental progress and applications of metamaterials in millimeter wave or microwave, and many usefully potential applications of terahertz as well, but still need considerable efforts to fill this “THz-gap” in future. Therefore, it is especially important to design the metamaterials device in the terahertz frequency regime. For the first, we analyze the split ring resonators(SRRs) model in theory, and many planar SRR arrays with different periodic structures have been designed for later testing, the planar SRR arrays are fabricated using conventional photolithography and electron-beam deposition of gold on n-GaAs substrate, the metal array and n- GaAs together form a Schottky contact. Then the influences of background substrate and the shapes of the SRRs on the terahertz resonance are experimentally investigated at several terahertz frequencies of continuous wave terahertz laser in turn, and all the transmission properties are recoded and analyzed. These metamaterials may be useful for future applications in the construction of various THz filters, THz antenna, or THz grid structures ideal for constructing THz switching devices.
Imaging detector research on terahertz (1 THz=10<sup>12</sup>Hz) wavelength region is a hot topic in recent years. So far, the terahertz wave has shown considerable application potential in advanced imaging of some special targets<sup>1</sup>. The terahertz imaging has a relatively high resolution correspondent to common radio frequency imaging. It takes object surface shape and internal structure information<sup>2</sup>, which can not be captured by current mature optics imaging means or conventional infrared imaging methods. However, for a long time, due to the lack of effective terahertz detection techniques<sup>3</sup> as well as most materials in nature inherently do not respond to THz radiation, or demonstrate a very weak response even not be utilized, it limits the development of terahertz theory and related technologies and applications especial in the terahertz detection fields, and thus leading to the progress and applications in THz regime lagging behind the rapid development of other electromagnetic spectrum. To realize the useful potential detecting applications of THz radiation, considerable efforts are underway for filling the ‘THz gap’. Some new type of materials such as typical metamaterial are really needed for constructing detecting architectures.<p> </p>Metamaterials<sup>4</sup>, which are artificially structured material, consists of subwavelength metallic resonators within or onto a dielectric or semiconducting substrate. Research and applications<sup>5,6</sup> show that they already exhibit attractive electromagnetic properties, which are not available in naturally materials. Therefore, they can be used to enhance the optoelectronic response ability so as to efficiently manipulate, control, and detect electromagnetic radiation by particularly designed metamaterial micro-nano-structure. In addition, by scaling their size, we can scale their response from radio frequency to optical wavelength region, which means we can design metamaterials detector operated at desired frequency in a very wide frequency range, for example from UV-IR-Microwave-RF, but in THz region is our key topic content in this paper.<p> </p>As demonstrated that metamaterials can be used to remarkably response incident THz radiation with both electric and magnetic resonant mode<sup>7</sup>, metamaterials micro-nano-structures are potential for future THz detection. By constructing metamaterials detectors for relatively wide THz wave, we can realize THz sensing and further imaging. In this paper, we design and simulate an electrically resonant terahertz metamaterial sensing unit. This kind of metamaterial micro-nano-structure can present an obvious response at 0.78 THz with a strong electrical resonant at the split-ring resonator（SRR） gap, and thus provides a possibility to obtain the electrical signal so as to achieve THz sensing. By analyzing the simulation results, we summarize the feasibility of terahertz detection, and come out a layout of terahertz detector by scaling the size of metamaterial detector unit, we can obtain unit detector architecture that also resonant at other frequencies and finally lead to realize multispectral imaging.