passive metamaterial structures
TRANSCRIPT
Outline Introduction Theory Citations
Passive Metamaterial Structures
Donovan Shickley
NCSUAdvisor Dr. Ralph Smith
RTG funded by NSF
April 20, 2009
Donovan Shickley Passive Metamaterial Structures
Outline Introduction Theory Citations
1 IntroductionDefinitionApplications
2 TheoryMaxwellRefraction IndexSuper LensSRRsCloaking
3 Citations
Donovan Shickley Passive Metamaterial Structures
Outline Introduction Theory Citations Definition Applications
Definition of a Metamaterial
materials engineered to have properties not found innaturally occurring materialsleft-handed material: has negative index of refractionperiodic structure of cells (i.e. SRRs, swiss rolls)
Donovan Shickley Passive Metamaterial Structures
Outline Introduction Theory Citations Definition Applications
Metamaterial Applications
super lensessurpass the diffraction limit
invisibility cloaks, stealth technologyimproved antennae capabilities
arbitrarily small cell phones
magnetic resonance imaging, ultrasoundmany more to be discovered
Donovan Shickley Passive Metamaterial Structures
Outline Introduction Theory Citations Maxwell Refraction Index Super Lens SRRs Cloaking
Brief description of Maxwell’s Equations
Four partial differential equations that describe magneticand electric fields and their interactionsTwo of the equations describe the propagation of lightthrough homogeneous material
where E = electric field, H = magnetic field,µ = magnetic permeability, and ε = electric permittivity
Donovan Shickley Passive Metamaterial Structures
Outline Introduction Theory Citations Maxwell Refraction Index Super Lens SRRs Cloaking
Material Space
All materials categorized based on electric permittivityversus magnetic permeability
Third quadrant corresponds to negative index of refractionmaterials
Donovan Shickley Passive Metamaterial Structures
Outline Introduction Theory Citations Maxwell Refraction Index Super Lens SRRs Cloaking
Indices of Refraction
N = ±√εµ
Snell’s Law: n1 sin θ1 = n2 sin θ2
n=0 n=1.2 n=-1.2
left-handed material (LHM): E, B, wave vector folllow aleft-hand rulewave propagates in opposite direction of energy
Donovan Shickley Passive Metamaterial Structures
Outline Introduction Theory Citations Maxwell Refraction Index Super Lens SRRs Cloaking
Creating a Super Lens
The imaging size of traditional lenses is determined by thediffraction limit
proportional to wavelength of light over diameter of lens
Veselago lens created in 2008 that can image 10x betterthan current (Grbic, Merlin at University of Michigan)
Donovan Shickley Passive Metamaterial Structures
Outline Introduction Theory Citations Maxwell Refraction Index Super Lens SRRs Cloaking
Split-Ring Resonators
single metamaterial unitscale much less than wavelengthof radiationnegative µeff
magnetic flux induces current"splits" produce largecapacitance valueshigh capacitance leads tolower resonating frequency
dimensions of SRR decidesresonant wavelength
Donovan Shickley Passive Metamaterial Structures
Outline Introduction Theory Citations Maxwell Refraction Index Super Lens SRRs Cloaking
The Basics of Cloaking
Schurig 2006: first experimental demonstration ofmetamaterial cloaking at microwave frequency
concentric rings ofperiodically-structuredpassive metamaterialelements (SRRs)
Donovan Shickley Passive Metamaterial Structures
Outline Introduction Theory Citations Maxwell Refraction Index Super Lens SRRs Cloaking
Limitations
passive metamaterial structures exhibitsignificant losses by absorbing energy from EM wavesstrongly frequency dependent properties means useful onlyfor narrow bandwidth applications
active metamaterial structuresdynamic frequency resonance or wide bandwidthreal-time control and manipulation of radiation
Donovan Shickley Passive Metamaterial Structures
Outline Introduction Theory Citations
Pendry, JB, Holden, AJ, Robbins, DJ, Stewart, WJ. 1999.Magnetism from Conductors and Enhanced Non-LinearPhenomena. Microwave Theory and Techniques, IEEETransactions. vol 47, iss 11: pp 2075-2084.Schurig, D et al. 2006. Metamaterial Electromagnetic Cloak atMicrowave Frequencies. Science. vol 314, no 5801: pp 977-980.Greenleaf, A, Kurylev, Y, Lassas, M, Uhlmann, G. 2009.Cloaking Devices, Electromagnetic Wormholes, andTransformation Optics. SIAM Review. vol 51, no 1: pp 3-33.Smith, David. Novel Electromagnetic Materials. Research Groupof David R Smith. Duke University. 20 April 2009.Chen, HT et al. 2006. Active Terahertz Metamaterial Devices.Nature. vol 444: pp 597-600.
Donovan Shickley Passive Metamaterial Structures