1. Metamaterials - Concept and Applications
Dr Vesna Crnojević-Bengin
Faculty of Technical Sciences
University of Novi Sad
March 2006

2. Overview Microwave passive circuits Metamaterials LH metamaterials
Definition
Examples
LH metamaterials
Idea
Phenomena
Realization
LH microstrip structures
Resonant and non-resonant structures
Applications

3. Microwave Passive Circuits
Rationale

4. Problem Dimensions  Performances End-coupled ms resonator:
Antennas: narrow beam with only one source element?
Classical theory: large source
Metamaterials: ENZ substrate

5. Antenna on ENZ Substrate

6. Characteristics Definition Types Examples
Metamaterials
Characteristics
Definition
Types
Examples

7. Material Characteristics
Rel. permitivity εr
Rel. permeability μr
Rel. index of refraction
Rel. characteristic impedance

8. Extreme values of εr and μr
Metamaterials:
EVL – Epsilon Very Large
ENZ – Epsilon Near Zero
MVL – Mu Very Large
MNZ – Mu Near Zero
MENZ – Mu and Epsilon Near Zero
HIMP – High Impedance
LIMP – Low Impedance
HIND – High Index
LIND – Low Index μr εr

9. Definition
Metamaterials are artificial structures that exhibit extreme values of effective εr i μr.

10. Example – HIMP and LIMP

11. Metamaterials Do Not Exist
Artificial materials
Periodic structures
Period much smaller then λ
 Homogenization of the structure
 Effective values of εr and μr

12. Examples of Metamaterials

13. First Ideas Development Realization Applications
Left-Handed MM
First Ideas
Development
Realization
Applications

14. Other Quadrants? μr εr Single-negative MM: εr<0 or μr<0
evanescent
mode
propagation
mode
(isotropic dielectrics) εr
evanescent
mode
(ferrites)

15. ? Veselago’s Intuition μr εr Double-negative MM: εr<0 and μr<0 ?
evanescent
mode
propagation
mode
(isotropic dielectrics) εr ?
evanescent
mode
(ferrites)

16. Conditions of Existence
No law of physics prevents the existence of DN MM
Generalized entropy conditions for dispersive media must be satisfied ( )

17. Veselago’s Conclusions
Propagation constant β is real & negative
 Propagation mode exists
 Antiparalel group and phase velocities
 Backward propagation (Left-hand rule)
 Negative index of refraction

18. Synonyms Double-Negative (DN) Left-Handed (LH)
Negative Refraction Index (NRI)
(Metamaterials)

19. Left-Handed Metamaterials
Double-negative MM: εr<0 and μr<0 μr
evanescent
mode
propagation
mode
(isotropic dielectrics) εr
propagation
mode
(Left-Handed MM)
evanescent
mode
(ferrites)

20. Apparent Paradox Group velocity increases with frequency
 superluminal propagation ?!?
Explanation:
LH MM is a dispersive media, where:
Pulse can be superluminally propagated
Group velocity does not bear a well defined physical meaning
Velocity relevant to energy propagation is not group velocity but front velocity, always smaller then c

21. Consequences of LH MM Phenomena of classical physics are reversed :
Doppler effect
Vavilov-Čerenkov radiation
Snell’s law
Lensing effect
Goss-Henchen’s effect

22. Snell’s Law
!!!

23. Lenses
Direct consequence of reversed Snell’s law

24. But Alas... Everything so far was “what if”...
Can single- or double-negative materials really be made?

25. First SN MM – J. B. Pendry
εr< μr<

26. Why is r negative? Plasmons – phenomena of excitation in metals
Resonance of electron gas (plasma)
Plasmon produces a dielectric function of the form:
Typically, fp is in the UV-range
Pendry: fp=8.2GHz

27. Why is μr negative?

28. Experimental Validation
Smith, Shultz, et al

29. Resonant and non-resonant structures Applications
LH MS Structures
Resonant and non-resonant structures
Applications

30. Resonant LH Structures
Split Ring Resonator (SRR)
 Very narrow LH-range
 Small attenuation
Many applications, papers, patents
Super-compact ultra-wideband (narrowband) band pass filters
Ferran Martin, Univ. Autonoma de Barcelona

31. Wide Stopband
Garcia-Garcia et al, IEEE Trans. MTT, juni 2005.

32. Complementary SRR Application of Babinet principle - 2004.
CSRR gives ε‹0

33. LH BPF – CSRR / Gap November 2004. Gaps contribute to μ‹0
Low attenuation in the right stopband

34. BPF – CSRR / Stub
August 2005.
90% BW
Not LH!!!

35. Three “Elements” CSRR/Gap – steep left side
CSRR/Stub – steep right side
2% BW

36. Multiple SRRs and Spirals
Crnojević-Bengin et al, 2006.

37. Fractal SRRs
Crnojević-Bengin et al, 2006.

38. Non-Resonant LH Structures
June 2002.
Eleftheriades
Caloz & Itoh
Oliner
Transmission Line (TL) approach
Novel characteristics:
Wide LH-range
Decreased losses

39. Conventional (RH) TL
Microstrip

40. LH TL
Dual structure

41. !!! = A Very Simple Proof Materials: LH TL:
Analogy between solutions of the Maxwell’s equations for homogenous media and waves propagating on an LH TL
Materials: LH TL: =
!!!

42. Microstrip Implementation
Unit cell

43. Dispersion Diagrams
RH TL LH TL

44. Is This Structure Purely LH?
Unit cell

45. CRLH TL
Real case – RH contribution always exists

46. LH TL Characteristics Wide LH-range
Caloz, Itoh, IEEE AP-S i USNC/URSI Meeting, juni 2002.

47. 2-D LH Metamaterials

48. Applications of LH MM Guided wave applications
Filters
Radiated wave applications
Antennas
Refracted wave applications
Lenses

49. Guided Wave Applications
Dual-band and enhanced-bandwidth components
Couplers, phase shifters, power dividers, mixers)
Arbitrary coupling-level impedance/phase couplers
Multilayer super-compact structures
Zeroth-order resonators with constant field distribution
Lai, Caloz, Itoh, IEEE Microwave Magazin, sept

50. Dual-Band CRLH Devices
Second operating frequency:
Odd-harmonic - conventional dual-band devices
Arbitrary - dual-band systems
Phase-response curve of the CRLH TL :
DC offset – additional degree of freedom
 Arbitrary pair of frequencies for dual-band operation
Applications:
Phase shifters,
matching networks,
baluns, etc.

51. Dual-Band BLC Lin, Caloz, Itoh, IMS’03.
Conventional BLC operates at f and 3f
RH TL replaced by CRLH TL
 arbitrary second passband

52. CµS/CRLH DC Caloz, Itoh, MWCL, 2004.
Conventional DC:
 broad bandwidth (>25%)
 loose coupling levels (<-10dB)
CRLH DC:
 53% bandwidth
 coupling level −0.7dB

53. ZOR Sanada, Caloz, Itoh, APMC 2003.
Operates at β=0
Resonance independent of the length
Q-factor independent of the number of unit cells

54. SSSR Crnojević-Bengin, 2005.
LZOR=λ/5
LSSSR=λ/16
Easier fabrication
More robust to small changes of dimensions

55. Radiated Wave Applications
1-D i 2-D LW antennas and reflectors
ZOR antenna, reduced dimensions
Backfire-to-Endfire LW Antenna
Electronically controlled LW antenna
CRLH antenna feeding network

56. Backfire-to-Endfire LW Antena
Operates at its fundamental mode
Less complex and more-efficient feeding structure
Continuous scanning from backward (backfire) to forward (endfire) angles
Able to radiate broadside
Liu, Caloz, Itoh, Electron. Lett., 2000.

57. Electronically Controlled LW Antenna
Frequency-independent LW antenna
Capable of continuous scanning and beamwidth control
Unit cell:
CRLH with varactor diode
β depends on diode voltage

58. Antenna Feeding Network
Itoh et al, EuMC 2005.

59. Refracted Wave Applications
Most promising
Not much investigated - 2-D, 3-D
Negative focusing at an RH–LH interface
Anisotropic metasurfaces
Parabolic refractors...

60. Current Research... Subwavelength focusing:
Grbic, Eleftheriades, 2003, (Pendry 2000):
NRI lense with εr=−1 and µr=−1 achieves focusing at an area smaller then λ2
Anisotropic CRLH metamaterials:
Caloz, Itoh, 2003.
PRI in one direction, NRI in the orthogonal
Polarization selective antennas/reflectors

61. Future Applications Miniaturized devices based ZOR
MM beam-forming structures
Nonlinear MM devices for generation of ultrashort pulses for UWB systems
Active MM - dual-band matching networks for PA, high-gain bandwidth distributed PA, distributed mixers
Refracted-wave structures – compact flat lenses, near-field high-resolution imaging, exotic waveguides
SN MM – ultrathin waveguides, flexible single-mode thick fibers, very thin cavity resonators
Terahertz MMs – medical applications
Natural LH MM – currently not known to exist
SF MM - chemists, physicists, biologists, and engineers tailor materials missing in nature

62. Main Challenges
Wideband 3-D isotropic LH meta-structure

63. Main Challenges
Development of fabrication technologies (LTCC, MMIC, nanotechnologies)
Development of nonmetallic LH structures for applications at optical frequencies
Miniaturization of the unit cell
Development of efficient numerical tools

64. “LH materials … one of the top ten scientific breakthroughs of 2003.”
Conclusion
“LH materials … one of the top ten scientific breakthroughs of 2003.”
Science, vol.302, no.5653, 2004.
“MMs have a huge potential and may represent one of the leading edges of tomorrow’s technology in high-frequency electronics.”
Proc. of the IEEE, vol.93, no.10, Oct.2005.