Abstract-Terahertz surface plasmon waveguide based on a one-dimensional array of silicon pillars

Gagan Kumar1,3, Shanshan Li2, Mohammad M Jadidi2 and

Thomas E Murphy1,2

1 Institute for Research in Electronics and Applied Physics, University of

Maryland, College Park, MD 20742, USA

2 Department of Electrical and Computer Engineering, University of Maryland,

College Park, MD 20742, USA

E-mail: gkm2010@umd.edu

New Journal of Physics 15 (2013) 085031 (11pp)

Received 24 April 2013

Published 28 August 2013

Online at http://www.njp.org/

doi:10.1088/1367-2630/15/8/085031

http://m.iopscience.iop.org/1367-2630/15/8/085031/pdf/1367-2630_15_8_085031.pdf

Abstract. We experimentally demonstrate a three-dimensional plasmonic

terahertz waveguide by lithographically patterning an array of sub-wavelength

pillars on a silicon substrate. Doped silicon can exhibit conductive properties

at terahertz frequencies, making it a convenient substitute for conventional

metals in plasmonic devices. However, the surface wave solution at a doped

silicon surface is usually poorly confined and lossy. Here we demonstrate that

by patterning the silicon surface with an array of sub-wavelength pillars, the

resulting structure can support a terahertz surface mode that is tightly confined

in both transverse directions. Further, we observe that the resonant behavior

associated with the surface modes depends on the dimensions of the pillars, and

can be tailored through control of the structural parameters. We experimentally

fabricated devices with different geometries, and characterized the performance

using terahertz time-domain spectroscopy. The resulting waveguide characteristics
 are confirmed using finite element numerical simulations, and we further show that
 a simple one-dimensional analytical theory adequately predicts the observed dispersion
 relation.