Dielectric-Metal Structures for Terahertz Plasmon Waveguiding

Terahertz frequency range is highly demanded nowadays for applications in sensing, security and communications. The lack of transparent enough materials for THz waves delivery is a big and unsolved problem. Only dry air and metal surface are good candidates. But plasmons exhibit very low coupling to any metal in THz because metals are almost ideal conductors here[1,2]. We suggest to combine thin dielectric wires and metal surface for low loss THz radiation propagation. In appropriate configuration most of the propagating mode will be in the air gaps between dialectic and metal, thus we avoid high material losses in dielectric and radiation losses for bare metal.

First we simulate THz plasmons propagation on metal with small dielectric cylinders on it in COMSOL software, then made experiment with self made polymer fibers on Al surface.

The most transparent polymers known at present allow only tens of cm of THz propagation we chose polypropylene and Topas as the best materials for the fibers [3].

Our typical THz time-domain apparatus [2], it is based on femtosecond laser pulses conversion into THz frequency. We demonstrated that undistorted short THz pulse can be delivered on tens of cm distance without much attenuation and in the broad (0.1-2.5 THz) frequency range. Since the wavelength changes an order of magnitude (roughly form 3 mm to 100 microns), only central part of the spectra can fit to optimal waveguide dimensions. For optimal frequency, effective absorption coefficient can be reduced twice in comparison with both bare metal [4] or bulk dielectric[3].

Acknowledgment: The work is partly supported by RFBR grants: 14-02-00846.

[1] M. Gong, T.-I. Jeon, D. Grischkowsky, OPTICS EXPRESS, 17, pp. 17088-17101 (2009)

[2] Nazarov M.M., Shkurinov, A.P; Ryabov, A.Y; Bezus, E.A., IRMMW-THz2010, TECHNICAL DIGEST on CD, We-P.47

[3] E.V. Fedulova, M. M. Nazarov, A.A. Angeluts, et al, Proc. of SPIE Vol. 8337 pp. 83370I-(1-9) 2012

[4] M. Nazarov, J.-L. Coutaz, A. Shkurinov, F. Garet, Optics Communications, “, vol. 277, pp. 33–39, (2007).

maxim@lasmed.phys.msu.ru