Terahertz composite right-left handed metamaterials

Benjamin S. Williams1,2, Zhijun Liu1,2, Philip W. C. Hon1, Amir Ali Tavallaee1,2, QiSheng Chen3, Tatsuo Itoh1

1Department of Electrical Engineering, University of California Los Angeles, CA 90095 2California NanoSystems Institute (CNSI), University of California Los Angeles, CA 90095

3Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278

We present the development of 1D composite right-left handed (CRLH) transmission-line metamaterial structures in the terahertz frequency range. A conventional transmission line is described by a shunt capacitance CR and a series inductance LR, and exhibits right-handed (forward-wave) propagation only. A CRLH transmission line is obtained by loading the transmission-line with a series capacitance CL and a shunt inductance LL [1]. Proper choice of the lumped element values (LLCR=LRCL ) achieves the “balanced” condition, where there is a smooth transition between right handed and left-handed (backwards wave) propagation. CRLH structure have been used in the microwave frequency range to demonstrate a variety of a of guided-wave devices (i.e. multi-band and enhanced bandwidth components, power combiners/splitters, compact resonators), as well as radiated-wave devices (i.e. 1D and 2D resonant and leaky-wave antennas). We have demonstrated 1D THz metal-insulator-metal waveguides engineered to exhibit CRLH behavior. Angle-resolved FTIR reflection spectroscopy is used to map the dispersion relation the leaky-wave regime. Left-handed dispersion is observed, and for properly designed structures, near-balanced operation is achieved. Tuning of the waveguide dispersion is achieved by varying the effective lumped element series capacitance. The response is strongly polarization dependent – while TE incident light couples to the CRLH modes, TM polarized light couples to a waveguide mode which exhibits right-handed only behavior. We explain this response, as well as the radiative damping, in terms of a cavity antenna model. These CRLH waveguide arrays may be useful for frequency selective surfaces, reflectarray antenna elements, or amplitude/phase modulators. We also discuss the implementations and applications of CRLH waveguides with THz quantum-cascade laser gain material, and their use as leaky-wave antennas [2, 3].

(a) (b) Fig. 1. (a) SEM image of array of CRLH metal-insulator-metal waveguides. Inset shows the effective transmission line model for one unit cell. (b) Incident angle dependent reflection spectra taken for TE incidence. Inset shows extracted dispersion relation, with color scale indicating absorption magnitude (red = maximum).

References

[1] A. Lai, C. Caloz, and T. Itoh, "Composite Right/Left-Handed Transmission Line Metamaterials," in IEEE

Microwave Magazine, September 2004, pp. 34-50. [2] A. A. Tavallaee, B. S. Williams, P. W. C. Hon, T. Itoh, and Q.-S. Chen, "Terahertz quantum-cascade laser

with active leaky-wave antenna," Appl. Phys. Lett., vol. 99, p. 141115, 2011. [3] A. A. Tavallaee, P. Hon, K. Mehta, T. Itoh, and B. S. Williams, "Zero-Index Terahertz Quantum-Cascade

Metamaterial Lasers," IEEE J. Quantum Electron., vol. 46, pp. 1091-1098, 2010.

Speaker: Benjamin S. WilliamsSession: Laser and LED PhysicsSee program for placement.

PQE-2012 Abstract Processed 08 December 2011 0