We study the presence of dark and bright modes in a planar metamaterial with a double rod unit cell introducing geometric asymmetry in rod lengths. The dark mode displays a Fano-type resonance with a sharp asymmetric profile, rendering it far more sensitive than the bright mode to slight variations of the dielectric environment. This peculiar feature may envisage the possible application of the asymmetric dimer metamaterial as an optical sensor for chemical or biological analysis, provided that the effect of material losses on the dark mode quality factor is properly taken into account.
Di Gennaro, E.; Gallina, I.; Andreone, A.; Castaldi, G.; Galdi, V. Experimental evidence of cut-wire-induced enhanced transmission of transverse-electric fields through sub-wavelength slits in a thin metallic screen. Opt. Express 2010, 18, 26769–26774.
Christ, A.; Martin, O.J.F.; Ekinci, Y.; Gippius, N.A.; Tikhodeev, S.G. Symmetry breaking in a plasmonic metamaterial at optical wavelength. Nano Lett. 2008, 8, 2171–2175.
[5]
Papasimakis, N.; Fu, Y.H.; Fedotov, F.A.; Prosvirnin, S.L.; Tsai, D.P.; Zheludev, N.I. Metamaterial with polarization and direction insensitive resonant transmission response mimicking electromagnetically induced transparency. Appl. Phys. Lett. 2009, 94, 211902–211904.
[6]
Singh, R.; Al-Naib, I.A.I.; Koch, M.; Zhang, W. Sharp Fano resonances in THz metamaterials. Opt. Express 2011, 19, 6314–6319.
[7]
Cao, W.; Singh, R.; Al-Naib, I. A.I.; He, M.; Taylor, A.J.; Zhang, W. Low-loss ultra-high-Q dark mode plasmonic Fano metamaterials. Opt. Lett. 2012, 37, 3366–3368.
[8]
Luk'yanchuk, B.; Zheludev, N.I.; Maier, S.A.; Halas, N.J.; Nordlander, P.; Giessen, H.; Chong, C. The Fano resonance in plasmonic nanostructures and metamaterials. Nat. Mater. 2010, 9, 707–715.
[9]
Singh, R.; Rockstuhl, C.; Lederer, F.; Zhang, W. Coupling between a dark and a bright eigenmode in a terahertz metamaterial. Phys. Rev. B 2009, 79, 085111:1–085111:4.
[10]
Christ, A.; Ekinci, Y.; Solak, H.H.; Gippius, N.A.; Tikhodeev, S.G.; Martin, O.J.F. Controlling the Fano interference in a plasmonic lattice. Phys. Rev. B 2007, 76, 201405.
[11]
Wu, C.; Khanikaev, A.B.; Adato, R.; Arju, N.; Yanik, A.A.; Altug, H.; Shvets, G. Fano-resonant asymmetric metamaterials for ultrasensitive spectroscopy and identification of molecular monolayers. Nat. Mater. 2012, 11, 69–75.
[12]
Mousavi, S.H.; Khanikaev, A.B.; Neuner, B.; Fozdar, D.Y.; Corrigan, T.D.; Kolb, P.W.; Drew, H.D.; Phaneuf, R.J.; Alù, A.; Shvets, G. Suppression of long-range collective effects in meta-surfaces formed by plasmonic antenna pairs. Opt. Express 2011, 19, 22142–22155.
[13]
Dong, Z.-G.; Liu, H.; Xu, M.-X.; Li, T.; Wang, S.-M.; Zhu, S.-N.; Zhang, X. Plasmonically induced transparent magnetic resonance in a metallic metamaterial composed of asymmetric double bars. Opt. Express 2010, 18, 18229–18234.
[14]
Fedotov, V.A.; Rose, M.; Prosvirnin, S.L.; Papasimakis, N.; Zheludev, N.I. Sharp trapped-mode resonances in planar metamaterials with a broken structural symmetry. Phys. Rev. Lett. 2007, 99, 147401.
[15]
Lahiri, B.; Khokhar, A.Z.; de la Rue, R.M.; McMeekin, S.G.; Johnson, N.P. Asymmetric split ring resonators for optical sensing of organic materials. Opt. Express 2009, 17, 1107–1115.
[16]
Hao, F.; Sonnefraud, Y.; van Dorpe, P.; Maier, S.A.; Halas, N.J.; Nordlander, P. Symmetry breaking in plasmonic nanocavities: Subradiant LSPR sensing and a tunable Fano resonance. Nano Lett. 2008, 8, 3983–3988.
[17]
Liu, N.; Weiss, T.; Mesch, M.; Langguth, L.; Eigenthaler, U.; Hirscher, M.; Sonnichsen, C.; Giessen, H. Planar metamaterial analogue of electromagnetically induced transparency for plasmonic sensing. Nano Lett. 2010, 10, 1103–1107.
[18]
Pu, M.; Huang, C.; Hu, C.; Wang, C.; Zhao, Z.; Wang, Y.; Luo, X. Investigation of Fano resonance in planar metamaterial with broken translation symmetry. Opt. Express 2013, 21, 992–1001.
[19]
Kim, J. Joining plasmonics with microfluidics: From convenience to inevitability. Lab Chip 2012, 12, 3611–3623.
[20]
Escobedoab, C. On-chip nanohole array based sensing: A review. Lab Chip 2013, 13, 2445–2463.
[21]
Gallinet, B.; Martin, O.J.F. Ab initio theory of Fano resonances in plasmonic nanostructures and metamaterials. Phys. Rev. B 2011, 83, 235427.
[22]
Liu, N.; Langguth, L.; Weiss, T.; Kastel, J.; Fleischhauer, M.; Pfau, T.; Giessen, H. Plasmonic analogue of electromagnetically induced transparency at the Drude damping limit. Nat. Mater. 2009, 8, 758–762.
[23]
Zhang, S.; Genov, D.A.; Wang, Y.; Lui, M.; Zhang, X. Plasmon induced transparency. Phys. Rev. Lett. 2008, 101, 047401.
[24]
Zhang, S.; Bao, K.; Halas, N.J.; Xu, H.; Nordlander, P. Substrate-induced Fano resonances of a plasmonic nanocube: A route to increased-sensitivity localized surface plasmon resonance sensors revealed. Nano Lett. 2011, 11, 1657–1663.
[25]
Hao, F.; Nordlander, P.; Sonnefraud, Y.; van Dorpe, P.; Maier, S.A. Tunability of subradiant dipolar and Fano-type plasmon resonances in metallic ring/disk cavities: Implications for nanoscale optical sensing. ACS Nano 2009, 3, 643–652.
Prodan, E.; Radloff, C.; Halas, N.J.; Nordlander, P. A hybridization model for the plasmon response of complex nanostructures. Science 2003, 302, 419–422.
[28]
Sherry, L.J.; Chang, S.-H.; Schatz, G.C.; van Duyne, R.P. Localized surface plasmon resonance spectroscopy of single silver nanocubes. Nano Lett. 2005, 5, 2034–2038.
[29]
Homola, J. Surface Plasmon Resonance Based Sensors; Springer: Berlin, Germany, 2006.
[30]
Offermans, P.; Schaafsma, M.C.; Rodriguez, S.R.K.; Zhang, Y.; Crego-Calama, M. Universal scaling of the figure of merit of plasmonic sensors. ASC Nano 2011, 5, 5151–5157.
[31]
Reale, C. Optical constants of vacuum deposited thin metal films in the near infrared. Infrared Phys. 1970, 10, 173–181.
