12
/
QELS
2002
/ MONDAY MORNING
QMD
1 0 1 5 am-i2:00
pmRoom:
201Metamaterials
JrremylBaumberS Univ. of Southampton, UK, Presider
Q M D I 1 0 1 5 am
Mlcrowave Transmlsslon through Metamaterlals In Free Space K. Aydin, Mehmet Bayindir, and E. Ozboy, Department ofphysicr, Bilkcnt University, Bilkent, 06533 Ankara, Turkey, Email:
boyindi~~fen.bilkent.edu.rr
Recently, the composite metamaterials, which was first theoretic+ proposed by Veselago in 1968,' have inspired great attentions due to inter- esting hysical properties and novel applica- lions.'. "The electric and magnetic behaviors of materials are determined by two important mate- rial parameters, & (dielectric permittivity) and p (magnetic permeability). Together the perme- ability and the permittivity determine the re- sponse of the material to the electromagnetic ra- diation. Generally, E and
w
are both positive in ordinary materials. Negative dielectric medium a t microwave domain can be obtained by arrang- ing thin metallic wires periodically! Below plasma frequency, dielectric permittivity will take negative values. Pendry et al. proposed negative magnetic permeability by using special wnfigu-P.
0.5 mm.
QMDl Fig. 1. [Top panel] Schematic draw- ing of a single SRR with parameters l = 3 mm and d = t = w = 0.33 mm. [Bottom panel] The schematicr of wmposite metamaterial consisting of thin wires and SRRs. The structure is wnaiated of N, = 25, Ny = 25, and N, = 20 unit cells, and eachunitceUhasdimensionsa,=Smm,o,=3.63 mm, and as = 5 mm. The thickness of thin wire is
I . I
I 9 H 13
Frequency (Gtlz)
Q M D l Fig. 2. Measured transmission spec- tra corresponding to thin wires, SRRs, and meta- materials.
rations of metals, named as split ring resonator and swiss roll capacitor?
In order to investigate properties of metama- terials, we wnstructed a wmposite strmtuies which consists of periodical arrangement of thin copper wires and SRRson a circuit board (see Fig. I). We first measured the transmission spectra of the thin wire and SRR mediums individually. The measurements are performed in free space by wing a HP 8510C network analyzer and mi- crowave horn antennas. Figure 2 exhibits the measured transmission spectra of SRRS (dotted line), thin wires (dot-dashed line), and the w m - posite metamaterials (solid line). The SRR medium exhibits a stop band eaending from 8.7 to 10.3 GHz. The thin wire structure has a plasma frequency around 11.3 GHz. As shown in Fig. 2, there appears a transmission band for the w m - posite metamaterial within the stop bands of SRR and thin wire structures.
In summary, we investigated the transmission properties of composire metamaterials at mi- crowave frequencies. We observed that a pass- band is formed within the forbidden transmis- sion bands of thin wire and SRR s t r u ~ t ~ r e s .
References
1. V.G. Veselago,
"The
electrodynamics of sub- stances with Simultaneously negative values of&andp?Suv.Phys.Usp. 10,509(1968). 2. J.B. Pendry, A.J. Holden, D.J. Robbins, andW.J. Stewart, "Magnetism from onductorr and enhanced nonlinear phenomena? IEEE Trans. Microwave Theory Tech. 47, 2075 (1 999).
3. D.R.Smith,W.Padilla,D.C.Vier,S.C.Nemat-
Nasser, and S. Sihhultz, "Cdmposite medium with simultaneously negative permeability and permittivity? Phys. Rev. Lett. 84, 4184 4. J.B. Pendry, '"Negative refraction makes a perfectlensrPhys.Reu.Lett.85,3966 (2000). 5. R.A. Shelby,
D.R.
Smith, S.C. Nemat-Nasser,"Microwave transmission through a two-di- mensional, isotropic, leh-handed metamate- rial,"Appl. Phys. Lett. 78,489 (2001). 6. 1.B. Pendry, A.J. Holden, D.J. Robbins, and
W.I. Stewart, "Low frequency plasmons in thin-wire structures,"]. Phy.: Cond. Matter, 10,4785 (1998).
(2000).
QMD2 1030 am
Chlral Gratlngs-a New Class of Polarlzatlon Sensltlve Metamaterlals
N.I. Zheludev and HI. Coles, Department of Physics and Astronomy, University of Southampton, SO17 IBJ, UK, Email: n.i.zheludeveioton.acuk
A. Ports, A. Papakortos and D.M. Bagnafl, Department oJElectronicr and Computer Science, UniverrityofSouthampton, SO17 IBI, UK
R. G e e j Department ofchemirtry, University of Southampton, SO17 IBJ, UK
Recently a new group of layered planar and quasi- planar metamaterials has emerged which prom- ise unique polarization characteristics. Metallic bilayered structures with chirality and inductive coupling are predicted' to show huge optical p- larization rotatory power resembling that of liq- uid crystals. The semi-chip1 planar gratings de- scribed here belong t o a distinctively different
d a s s of 2D StruCtllreS known as planar chiral ~truCtures.2 By definition, two planar chiral ob- jects of different chirality cannot be brought into congruence, unless they are lifted out of the plane by rotating by 180' about an axis in the plane of the structure. A gammadion is an example of such an object. It was expected that planar chiral structures would have pronounced polarization properties when interacting with light," however, to the best of our knowledge, this has never been confirmed experimentally. Here we report what we believe is the first experimental demonstra- tion of such polarization activity.
Gold semi-planar chiral gratings were manu- factured on silicon substrates using a wmbina- tion of direct-write electrun beam lithography and either ion beam milling or a lift-off process. We have manufactured two-dimensional gratings consisting of regular square patterns of gamma- d i m s or anti-gammadians. We have studied a
range of gratings with differem pitches, confain- ing gammadians of vations chakteristic sizes ranging from 700 nm t o 4 pm, and different senses of chirality aS illustrated on Fig. 1. A typi- cal grating has an area of approximately 1.0 x 1.0 mm', with a densityof gammadians of between 6 x IO5 cm' and 6 x IO6 cm?.
These gratings show a well-defined recta&
br
diffraction pattern as illustrated in Fig. 2. The polarization properties of the diffracted waves have been investigated at a wavelenah 06632 nm for S and P polarizatiohs at an angle of incidence of 60". The polarization state of the diffracted beams war fo.md to be different from that of the incident beam. In general the diffracted beams become elliptically polarized and the polarization azimuth rotates. Rotationi in excess of 30' were seen. It should be noted that for S and P incident polarizations no polarization change is expected on reflection from an isotropic unstructured in- terface. For a given diffraction order the polariza- tion azimuth rutation was found to have opposite sign for samples. which only differ in their hand- edness. On the same sample different diffraction orders show different polarization azimuth rota- tion, as illustrated in Fig. 2.Another startling feature of these samples has been their ability to alter the perceived wlor of reflected light when viewed through a low magni- fication polarizing microscope, even though the typical feature sizes of there structures are much
