Metamaterials and Their Applications
1. Flat Lens Modelling and Layered LHM Structures
Left-handed materials (LHMs) are those engineering composites that the electric permittivity and the magnetic
permeability of a material are both negative. This was noted theoretically a while ago; in 1968, Victor
Veselago  of the Lebedev Physics Institute in Moscow concluded LHMs exhibiting an anti-parallel nature in
its wave and Poynting vectors which is opposite to conventional materials that normally electromagnetic
waves carry energy in the same direction as they propagate, following what's called a right-hand rule. Exciting
possible electrodynamic properties, such as reverse Doppler shift, Cherenkov radiation and inverse Snell effect,
were identified. But his idea was forgotten because of the unavailability of LHMs at that time and until recently,
Pendry et al  demonstrated that materials with an array of split ring resonators (SRRs) produce negative
permeability over certain frequency bands. Soon afterwards, by combining a two-dimensional (2D) array of
SRRs interspersed with a 2D array of wires, Smith et al  demonstrated for the first time the existence of
Figure 1. Dispersive FDTD Simulation at QMUL verifying possible construction of Perfect Lens
from LHMs predicted by Pendry 
Figure 2. A snapshot of the near field (Ez) image through a multi-layer LHM slab
2 . Wire Medium Imaging
We have investigated, through numerical simulation whether or not the finite transverse dimensions of LHM slabs
influence the quality of their sub-wavelength imaging. However, in practice, the fabrication of left-handed media
remains problematic, since it requires the creation of negative permeability, which does not exist in nature.
Furthermore, currently available designs of the left-handed media are very lossy at both microwave and optical
frequencies are very lossy, which restricts and even prevents their use in sub-wavelength imaging applications.
There is an alternative approach to sub-wavelength imaging in the sense of mapping the source distribution in
one plane onto another (the imaging plane). This approach involves neither the use of left-handed media nor does
it capitalize on negative refraction or amplification of evanescent waves, which has been referred to as
canalization. It is based on transporting both the propagating and evanescent spectra of a source by transforming
them into propagating waves inside a slab of specially designed materials. Then, these propagating modes are
capable of transporting sub-wavelength images from one interface of the slab to the other. The source must be
placed very close to the front interface of the slab in order to minimize the degradation of its spectrum which
occurs when the fields propagate in the free space. It is also necessary to minimize the reflection from the slab
via an appropriate choice of its thickness. This is done by tuning the slab thickness for Fabry-Perot resonance,
to reduce reflections from its interface for a wide range of angles of incidence, and minimize the interfering
interactions between the source and the slab that can distort the image. The material operating in the canalisation
regime should have a flat iso-frequency contour, implying that, it should support waves traveling in a certain
direction with fixed phase velocity for any transverse wave vectors. The materials that fulfil this requirement
are available at both microwave and optical frequency ranges. One such artificial material, is the wire medium
comprising of, a regular array of parallel metallic wires.
3. 95GHz Woodpile EBG Antennas
Millimetr e wave systems are becoming increasingly important in many applications because they can provide
wider bandwidth for transmitting large amount of data and better resolution in radar systems. Electromagnetic
Bandgap ( EBG ) structures, a class of metamaterial and also known as photonic bandgap structures (PBG) in
optics, are now finding numerous applications at microwave and millimetr e wave frequencies . The full potential
of EBG structures can be utili s ed with a full three dimensional (3D) bandgap. Thus rapid and cost-effective
fabrication techniques for 3D EBG structures are of significant importance. A woodpile structure shown in Fig. 1
exhibits a full 3D bandgap and can be easily fabricated for applications at microwave frequencies using columns
of individually machined dielectric rods . However, at millimetr e wave frequencies, conventional machining would
not be convenient because of small dimensions (50–500 m m). Various sophisticated techniques such as silicon
lithography are available for microstructures, but those are more appropriate for terahertz and photonic wavelength
applications, and would be costly to fabricate 3D structures with large number of layers for applications at W-band
(75-110 GHz). In this work, we present a direct rapid prototyping method for constructing 3D EBG materials for
millimetrewave applications, with a possible extension to higher frequencies based on extrusion freeforming of
ceramic materials. The proposed fabrication method can also be versatile for constructing curved geometries
and creating defects in layered structures.
1. Veselago, V.G., " The electrodynamics of substances with simultaneously negative values of and ,"
Sov. Phys. Usp., Vol.10, No.4, 509-514, Jan-Feb, 1968.
2. Pendry, J.B.; Holden, A.J.; Robbins, D.J.; Stewart, W.J. 'Magnetism from conductors and enhanced
nonlinear phenomena' Microwave Theory and Techniques, IEEE Transactions on, Volume: 47 Issue: 11,
Nov. 1999 Page(s): 2075 -2084
3. Smith, D.R.; W.J. Padilla; D. C. Vier; S. C. Nemat-Nasser, and S. Schultz, "Composite media with
simultaneously negative permeability and permittivity," Phys. Rev. Lett. , Vol.84, 4184-4187, 2000
4. Garcia N, Nieto-Vesperinas M, "Left-handed materials do not make a perfect lens", PHYS REV LETT
88 (20): art. no. 207403 MAY 20 2002
5. Y. Hao, L. Lu and C. G. Parini, 'Dispersive FDTD Modeling on Multi-layer Left-Handed Meta-Materials
for Near/Far Field Imaging At Microwave Frequencies', the 2003 IEEE AP-S International Symposium
on Antennas and Propagation and USNC/CNC/URSI North American Radio Science Meeting, Columbus,
Ohio, USA on June, 2003.
7. Chiyan Luo, Steven G.Johnson, and J.D. Joannopolous, J.B Pendry ‘Negative refraction without
negative index in metallic photonic crystals’, Optics Express, Vol.11,No.7, April 7, 2003
8. P.V Parimi, W.T.Lu, P.Vodo, J.Sokoloff, S.Sridhar, ‘Negative Refraction and Left-handed
electromagnetism in Microwave Photonic Crystals’, cond-mat/0306109, 2003
9. Y. Hao, S. Sudhakaran and C. G.Parini, ‘Spatial Harmonics Effects On Characterisation Of
Left-Handed Metamaterials’, Asia-Pacific Microwave Conference, orea, Nov., 2003.
For more information on our research, please contact Prof. Y. Hao .