Wireless Power Transmission Challenges for IoT Applications
Discussing challenges in ambient energy harvesting for IoT devices, including unstable ambient power and low energy harvested from RF signals. The use of dedicated power signals and energy sources to improve harvesting efficiency is explored.
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Electromagnetic spatial dispersion in periodic metamaterials Carlo Rizza1,2, Alessandro Ciattoni2 1Department of Science and High Technology, University of Insubria, Via Valleggio 11, 22100 Como, Italy 2CNR-SPIN, via Vetoio 10, 67100 L Aquila, Italy Email:carlo.rizza@aquila.infn.it Website: https://site.google.com/site/rizzacarlo81
Outline Brief introduction on Periodic Metamaterials Spatial dispersion: artificial chirality/bi-anisotropy & Artificial magnetism Homogenization theory: multi-scale approach 1D chiral metamaterials
Metamaterials Metamaterials are an arrangement of artificial structural elements, designed to achieve advantageous and/or unusual (electromagnetic) properties d
Periodic Metamaterials Effectively continuous metamaterials d Band Gap materials (photonic crystals) d Hyperbolic media d Bragg scattering Artificial Bianisotropy Artificial magnetism Spatial dispersion- optical nonlocality
Spatial dispersion ( ) V ( ) ( ) = D r d K r , ' r r E r ' ' Spatial dispersion- optical nonlocality d Second-order spatial dispersion Photonic crystals Weak Dispersive media Effectively continuous media d ( ) = + + D E E E 0 i ij j ijk k j iklj k l j Maxwell s equations are invariant with respect to transformation: ' , = + D D Q = i H H Q ' 1 ( !!) non magneticinclusions First-order spatial dispersion Bi-anisotropic response i c i c = = + T D E H B E H ' ', ' 0 0 Chiral tensor ( ) nonbi anisotropic inclusions !!
Homogenization theory A suitable homogenization theory is the key ingredient to develop metamaterials allowing to mold the flow of electromagnetic waves in unprecedented ways. Fast Slow ( ) R r ( ) = = R R / 1 d Macroscopic equations ', i i c Microscopic equations = = E H H D ' ' i D = = B = H E H H D , i i 0 0 0 0 + i c ( ) R E ( ) ( ) = ( ) ( ) ( ) , = + eff eff T eff = = + n A A r A r R D E H B E H , ' ', ' 0 0 0 0 n n = 0 n ( ) ( R = = E E e , f f R 0 0 j j i i j j New!!! ) ( ij ) eff = + = + , Q Q Q f ij ji ij ij i j 1 2 ( ij ) eff = + + k e f imn e mqn e f f 0 imj m jq ij m q n A. Ciattoni, C. Rizza, PHYSICAL REVIEW B 91, 184207 (2015)
2D chiral metamaterials ( Re in ) ( ) R = f R j j periodicboundary condition ( ) ( ij ) ( ijk ) ( ) eff eff eff = + + D E E E 0 i j k j iklj k l j i c ( ij ) ( ji ) ( ) eff eff eff = + ' ' j , D E H E 0 i j iklj k l j i c ( ij ) eff = + ' B E H 0 i j i A. Ciattoni, C. Rizza, PHYSICAL REVIEW B 91, 184207 (2015)
3D-2D chiral metamaterials 3D chirality: Aleft and right hand are mirror images of one another. Unlike a ball and its mirror image, a hand and its mirror image are not identical. Optical activity/ electromagnetic chirality Planar object is said to be 2D chiral if it cannot be brought into congruence with its mirror image unless it is lifted from the plane.2D chirality produces bi-anisotropic effects A. Papakostas et al., Optical Manifestations of Planar Chirality PRL 90, 107404 (2003)
1D chiral metamaterials 1 2 3 2 1 x = = x x 0 x x 0 x x x translation translation The reflected and shifted structure corresponds to the original structure The structure does not correspond to the original one whichever translation is applied !!!
1D chiral Metamaterials ( ) ( ) ( ) eff eff = + + = 2 2 , , , diag I 0 0 0 0 || 0 0 0 0 ( ) eff = Omega-type response 0 Periodic 3-layer structure volume fractions: f ( ) = = = = 0.18, 0.33, 1 , 25 f f f f d period nm 1 2 3 1 2 (1), (2), (3) Ag SiO PMMA 2 circular dichroism circular birefringence Epsilon-near-zero Enhancement !!! C. Rizza et al. PRL 115, 057401 (2015)
Conclusions Nonlocal homogenization theory in metamaterials 1D chirality & 1D chiral metamaterials THz reconfigurable all-optical metamaterials (in collaboration with THz group, University of Bari) Metasurfaces, high dielectric contrast,effects of second-order dispersion
Thanks for your attention Questions?
