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Superconducting Electromagnetic Metamaterials Steven M. Anlage, Michael Ricci, Nathan Orloff Fermilab 23 May, 2007 Work Funded by NSF/ECS-0322844 1 Negative Refraction: Consequences Left-Handed or Negative Index of Refraction Metamaterials e < 0 AND m < 0 Veselago, 1967 Propagating waves have index of refraction n < 0 Phase velocity is opposite to Poynting vector direction Negative refraction in Snell’s Law: n1 sinq1 = n2 sinq2 Flat lens with no optical axis “Perfect” Lens (Pendry, 2000) Reverse Doppler Effect Radiation Tension Converging Lens → Diverging Lens and vice-versa Reversed Čerenkov Effect RHM Cloaking Devices (Engheta, Leonhardt, Pendry, Milton) LHM RHM Flat Lens Imaging Point source V. G. Veselago, Usp. Fiz. Nauk 92, 517 (1967) [Eng. Trans.: Sov. Phys. Uspekhi 10, 509 (1968)] 2 “perfect image” Metamaterial vs Photonic Crystal wavelength l Metamaterial elementary units or “atoms” a Create an “effective medium,” using engineered “atoms,” with macroscopic eeff, meff, n properties a~l Photonic Crystal 3 Use constructive and destructive interference toengineer properties of light → (k ) band structure band gaps defect states negative group velocity … Superconducting Metamaterials How to make them: Step 1 All-Nb X-band waveguide + couplers Nb X-band waveguide (22.86 x 10.16 mm2) Tc = 9.25 K Thanks to P. Kneisel @ JLab Nb Wires 0.25 mm dia. Tc = 9.25 K Nb Wires 4.57 mm 10.2 mm 22.9 mm What are we doing? 4 Superconducting Metamaterials How to make them: Step 2 Nb film, ~ 200 nm thick 0.89 cm 3.0 cm k 0.154 mm E B 5 0.3 mm Nb SRR 200 nm thick on Quartz (350 mm) Tc = 8.65 K 2.36 mm Negative Index Passband in a Superconducting Metamaterial 10 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 216 SRRs out -60 -80 10.0 10.4 10.8 NM 0 Negative Index NIRof Refraction SC Normal Superconducting Metal a = 5.08mm a = 7.19mm -20 -40array wire plasma -60 edge -80 10 6 in temperature Overlap0of eeff <Increasing 0 and-20 meff < 0 to make -40 n < 0 |S21| (dB) Transmission 216 SRRs in a 12-cell wire array, 9 cm long 11 12 9 Frequency (GHz) 10 11 13 12 Metamaterials: Novel Applications Thin SubWavelength Cavity Resonators (Engheta, 2002) For a resonance in the z-direction: New possibility – zero net phase winding 2p k0 (n1d1 n2 d2 ) z RHM LHM n1>0 n2<0 p integer p = 0 “zeroth order resonance” 0th resonance condition independent of d1 + d2 and depends only on d1/d2 d1 n2 d 2 n1 Conducting planes p can also be a negative integer! 7 Implementation of an LHM Compact Waveguide Novel LHM Pass Band 2 cm Split-Ring Resonators (SRRs) Provide m < 0 at 350 MHz Transmission |S21| (dB) Waveguide e<0 e>0 Frequency (GHz) Hrabar, et al., 2005 Measured transmission |S21| parameter of miniaturized waveguide (a = 16 mm) filled with metamaterial based on capacitively loaded rings. The ordinary cutoff of the waveguide is 7 GHz, while the SRRs produce a LHM pass band at 350 MHz. 8 Conclusions Negatively Refracting Metamaterials offer opportunities for a new kind of optics Negative Index of Refraction Flat Lens Imaging Amplification of Evanescent Waves “Super Lenses” There are many new Emerging Applications Compact (dual TL) structures with enhanced performance Composite LHM/RHM materials with unique field structures New antenna structures Novel optics / NIR lithography Recovering Evanescent fields SC metamaterials papers: Appl. Phys. Lett. 87, 034102 (2005) Appl. Phys. Lett. 88, 264102 (2006) [email protected] 9 What Else Can Be Done? 77K 77 K C u@ RT HT S@ Rs () Higher Frequencies Smaller size “atoms” Low-Loss Limited only by SC gap frequency Nb: 2D/ħ ~ 1 THz HTS: 2D/ħ ~ 10 THz @ Cu 1 100 Size Scaling Frequency (GHz) Losses remain small as dimensions shrink Enhanced Inductance Tricks: Thinner films – Enhanced Kinetic Inductance Josephson Junctions – Enhanced and tunable inductance Novel Effects Unique to Superconductors: SQUID – the ultimate low-loss tunable SRR Josephson Junction Array collective dynamics 10 Metamaterials: Novel Applications Amplification of evanescent waves Super-resolution imaging Perfect absorber condition Reversed Doppler effect Tunable reflection phase properties New guided mode structures Reversed optics Compact size and light weight electromagnetic structures 11 Metamaterials: Novel Antennas Directional Antenna with n ~ 0 A point source embedded in a metamaterial with n~0 will produce a directed beam nearly normal to the metamaterial/vacuum interface. From [Enoch2002]. RHM Super-Efficient Electrically-small Dipole Antenna (ℓ << l) X Ant l RRad LHM 3 RHM X Ant l RRad LHM shell compensates Im[ZAnt] Factor of 74 improvement in PRad at 10 GHz with l/1000 antenna 12 Small dipole antenna Ziolkowski (2003) 3 Implementation of an LHM Compact Waveguide Novel LHM Pass Band 2 cm Split-Ring Resonators (SRRs) Provide m < 0 at 350 MHz Transmission |S21| (dB) Waveguide e<0 e>0 Frequency (GHz) Hrabar, et al., 2005 Measured transmission |S21| parameter of miniaturized waveguide (a = 16 mm) filled with metamaterial based on capacitively loaded rings. The ordinary cutoff of the waveguide is 7 GHz, while the SRRs produce a LHM pass band at 350 MHz. 13 Implementation of an LHM Compact Resonator Microstrip Resonators RHM Transmission Lines RHM/LHM/RHM Conventional RHM LHM Transmission Line (Dual structure) Both resonate at 1.2 GHz RHM/LHM/RHM resonator is 86% smaller Scher, et al., 2004 14 Negative Index Microwave Circuits Dual Transmission Lines with NIR concepts are leading to a new class of microwave devices Compact couplers, resonators, antennas, phase shifters have been demonstrated 1.9 GHz 0th-order resonator T. Itoh, et al., UCLA 15