Abstract-THz artificial dielectric isolator

R. Mendis,  M. Nagai,   W. Zhang,   D. M. Mittleman

http://ieeexplore.ieee.org/document/8066918/

We experimentally demonstrate an isolator suitable for the THz spectral regime. The isolator is designed by combining a polarizing beamsplitter with a quarter-wave plate, both based on the same artificial-dielectric technology. The artificial-dielectric medium comprises of a stack of 30 μm thick metal plates that form an array of parallel-plate waveguides. The isolator exhibits an isolation of 52 dB with an insertion loss less than one dB, at a frequency of 0.46 THz, which rivals the performance of commercially available Faraday isolators for optical wavelengths.

Abstract-Artificial Dielectrics: Ordinary Metallic Waveguides Mimic Extraordinary Dielectric

2Author(s)

Mendis, R. ; Rice University, Houston, TX 77005 United States ; Mittleman, D.

http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6954587&sortType%3Dasc_p_Sequence%26filter%3DAND%28p_IS_Number%3A6954433%29

Consider an electromagnetic wave propagating in the empty space between two parallel metal plates. This situation is often the first example of guided waves encountered by undergraduate students since the solutions (the guided modes) are analytic and easily obtained. And yet, this seemingly simple configuration can give rise to a number of interesting and even counterintuitive phenomena. For the set of modes with the electric field pointing parallel to the surfaces of the two metal plates, the region between the plates, though simply empty space, mimics the properties of a dielectric medium with a wave velocity yp different from c, that of waves in vacuum. The waveguide therefore can be described as an artificial dielectric [1] with an effective refractive index n=c/yp different from unity. In contrast to naturally occurring dielectrics for which n 2 1, n can have a value less than unity. These waveguide-based artificial dielectrics were first introduced in a small body of work by the microwave community about half a century ago [2]-[5]. As discussed here [6]-[10], the wavelength scaling that results when moving from the microwave region to the terahertz (THz) region results in more practical structural dimensions. This gives new life to these artificial dielectrics for a variety of novel and exotic applications in THz science and technology.

Abstract-An electrically driven terahertz metamaterial diffractive modulator with more than 20 dB of dynamic range

N. Karl¹, K. Reichel¹, H.-T. Chen², A. J. Taylor², I. Brener³, A. Benz³, J. L. Reno³, R. Mendis¹ and D. M. Mittleman¹

 HIDE AFFILIATIONS
1 Department of Electrical and Computer Engineering, Rice University, MS 378, Houston, Texas 77251-1892, USA
2 Center for Integrated Nanotechnologies, Los Alamos National Laboratory, P. O. Box 1663, MS K771, Los Alamos, New Mexico 87545, USA
3 Center for Integrated Nanotechnologies, Sandia National Laboratories, P. O. Box 5800, MS 1082, Albuquerque, New Mexico 87185, USA
Appl. Phys. Lett. 104, 091115 (2014); http://dx.doi.org/10.1063/1.4867276

http://scitation.aip.org/content/aip/journal/apl/104/9/10.1063/1.4867276

We design and experimentally demonstrate a switchable diffraction grating for terahertz modulation based on planar active metamaterials, where a Schottky gate structure is implemented to tune the metamaterial resonances in real-time via the application of an external voltage bias. The diffraction grating is formed by grouping the active split-ring resonators into an array of independent columns with alternate columns biased. We observe off-axis diffraction over a wide frequency band in contrast to the narrow-band resonances, which permits operation of the device as a relatively high-speed, wide-bandwidth, high-contrast modulator,with more than 20 dB of dynamic range.

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