🔬 Negative refractive index
Veselago prediction
n = -√(εr·μr) для negative εr, μr. Snell's law: negative refraction. Backward waves, reversed Doppler.
First demonstration
Smith (2000): SRR + wires. 10 GHz frequency. n ≈ -2.7. Left-handed materials (LHM).
Band structure
Bandgap, slow-light regime. Negative group velocity: vg < 0. Anomalous dispersion.
Applications
Lensing, cloaking, antennas. Superlens: perfect imaging. Subwavelength resolution.
🔬 Perfect lensing
Pendry lens
Negative index slab для subwavelength focusing. Evanescent waves amplification. Resolution < λ/2.
Surface plasmons
SPP resonance: evanescent coupling. Field enhancement ~10³-10⁶. Super-resolution.
Hyperlens
Cylindrical anisotropic media: magnification subwavelength features. λ ~ 400 nm → microscope resolution.
Super-resolution microscopy
STORM, PALM, STED. Metamaterial-enhanced: resolution < 10 нм. Optical nanoscopy.
🎭 Cloaking
Transformation optics
Coordinate mapping: cloaked region → free space. Maxwell's equations covariance. Material parameters.
Spherical cloak
Cylindrical → spherical transformation. Anisotropic ε, μ. R1 < r < R2. Ray bending.
THz cloaking
SRR-based: cloaks для THz. Experimental: 3-4 THz. Invisible для radar.
Broadband cloaks
Non-resonant approaches. Active cloaking. Losses: absorption, reflection. Practical challenges.
💎 Plasmonics
Surface plasmons
SPPs: ω² = c²k²(ε_m ε_d)/(ε_m + ε_d). Dispersion у metal-dielectric. Propagation length ~100 μm.
Localized SPPs
Nanoparticles (Au, Ag): localized modes. Mie scattering. LSPR: ~400-800 nm for Au spheres.
Field enhancement
E-field enhancement ~10³-10⁶. Hot spots. SERS: surface-enhanced Raman. Single-molecule detection.
Applications
SERS, biosensing, photovoltaics, data storage. Plasmonic circuits. Photonic chips.
🔬 Metamaterial design
Split-ring resonators
SRRs: magnetic response μ(ω). LC resonance: ω_LC ≈ 1/√(LC). Negative μ frequency bands.
Metal wires
Thin wires: Drude ε(ω). Plasma frequency ωp. Negative ε для ω < ωp.
Fishnet structures
Stacked metal-dielectric layers. Negative index broadband. NIM: negative index materials.
Effective medium
Homogenization: subwavelength structures → effective ε, μ. Maxwell Garnett, Bruggeman models.
🔬 Frequency regimes
Microwave
10 GHz: first demonstrations. SRRs + wires. Large structures, low losses. Antennas.
THz
0.3-30 THz: sensing gap. Plasmonic metamaterials. Cloaks, modulators.
Optical
Visible: fabricating challenges. Metal losses. Hyperbolic metamaterials. Super-resolution.
Losses
Metal absorption: Drude damping γ. Quality factor Q. Loss mitigation: gain, new materials.
📊 Графіки та діаграми
Drude model
ε(ω) для metals:
Negative ε: real part Re(ε) < 0. Metal dielectric function. Plasmon resonance.
SPP dispersion
Surface plasmon:
Light line ω/c: SPP above. Subwavelength confinement.
ε(ω) = 1 - ωp²/(ω(ω + iγ)) Де ωp ≈ 10¹⁶ рад/с (plasma frequency) γ ~ 10¹⁴ рад/с (damping) ε < 0 для ω < ωp
🧪 Практичні приклади
Приклад 1: First negative index
Smith (2000): SRR + wires. 10 GHz, n ≈ -2.7. Verification: refraction, phase velocity.
Приклад 2: THz cloak
SRR-based cloak: 3-4 THz. Cylindrical geometry. Ray bending, invisibility.
Приклад 3: SERS enhancement
Au nanoparticles: E-field ~10⁶. Single-molecule Raman. Plasmon hot spots.
Приклад 4: Hyperlens
Anisotropic cylindrical: λ → visible. Subwavelength magnification. Optical nanoscopy.
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Метаматеріали: штучна матеріальність
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