Plasmon induced transparency in cascaded π-shaped metamaterials

Microscopies Enabled by Photonic Metamaterials

In recent years, the biosensor research community has made rapid progress in the development of nanostructured materials capable of amplifying the interaction between light and biological matter. A common objective is to concentrate the electromagnetic energy associated with light into nanometer-scale volumes that, in many cases, can extend below the conventional Abbé diffraction limit. Dating back to the first application of surface plasmon resonance (SPR) for label-free detection of biomolecular interactions, resonant optical structures, including waveguides, ring resonators, and photonic crystals, have proven to be effective conduits for a wide range of optical enhancement effects that include enhanced excitation of photon emitters (such as quantum dots, organic dyes, and fluorescent proteins), enhanced extraction from photon emitters, enhanced optical absorption, and enhanced optical scattering (such as from Raman-scatterers and nanoparticles). The application of photonic metamaterials as a means for enhancing contrast in microscopy is a recent technological development. Through their ability to generate surface-localized and resonantly enhanced electromagnetic fields, photonic metamaterials are an effective surface for magnifying absorption, photon emission, and scattering associated with biological materials while an imaging system records spatial and temporal patterns. By replacing the conventional glass microscope slide with a photonic metamaterial, new forms of contrast and enhanced signal-to-noise are obtained for applications that include cancer diagnostics, infectious disease diagnostics, cell membrane imaging, biomolecular interaction analysis, and drug discovery. This paper will review the current state of the art in which photonic metamaterial surfaces are utilized in the context of microscopy.

Coupled metamaterial optical resonators for infrared emissivity spectrum modulation

We study the absorptivity of coupled metamaterial resonators in the mid-infrared range. We consider resonators supporting either a bright mode or a dark mode, introducing an additional degree of freedom for spectral modulation relative to bright modes alone. In a dark-bright coupled resonator system, we demonstrate tunable spectral splitting by changing the separation between resonators. We show via coupled mode theory that resonator separation can be mapped to coupling constant. We further introduce a dark-dark coupled resonator system, which gives rise to an emissive bright mode only in the presence of inter-resonator coupling. The dark-dark system yields a broadband emissivity that decays to zero exponentially with resonator separation, providing a design method for strong thermal emissivity control.

Analog of multiple electromagnetically induced transparency using double-layered metasurfaces

We reported an analog of electromagnetically induced transparency (A-EIT) featured by double transparent peaks in the spectrum. The A-EIT is realized by double-layered metasurface which consists of spoof localized surface plasmons (S-LSP) and cut-wire (CW)-square rings (SR) hybrid. Electric and magnetic S-LSP are excited as bright and dark modes respectively then couple with resonant modes of CW and SR simultaneously to achieve multiple A-EIT. Two bright modes of the electric S-LSP and SR are excited by external electric field directly that produce a bright-bright mode A-EIT. Moreover, the magnetic S-LSP, which cannot be excited by external field directly, is excited through near field coupling from CW, inducing another bright-dark mode A-EIT. Theoretical analysis with corresponding experiment in microwave band are introduced for better insights into physical essence of the double-peaks A-EIT.

Plasmon-Induced Transparency in an Asymmetric Bowtie Structure

Plasmon-induced transparency is an efficient way to mimic electromagnetically induced transparency, which can eliminate the opaque effect of medium to the propagating electromagnetic wave. We proposed an aperture-side-coupled asymmetric bowtie structure to realize on-chip plasmon-induced transparency in optical communications band. The plasmon-induced transparency results from the strong coupling between the detuned bowtie triangular resonators. Either of the resonator works as a Fabry-Perot cavity with compact dimensions. The transparent peak wavelength can be easily controlled due to its strong linear relation with the resonator height. The ratio of absorption valley to the transparent peak can be more than 10 dB. Moreover, with excellent linearity of shifting wavelength to sensing material index, the device has great sensing performance and immunity to the structure deviations.

Tailoring electromagnetically induced transparency with different coupling mechanisms

Tailoring electromagnetically induced transparency with two different coupling mechanisms has been numerically demonstrated. The results show that EIT based on simultaneous electric resonance and magnetic resonance has relatively larger coupling distance compared with that based on electric resonance near field coupling to magnetic resonance. The relatively large coupling distance is due to the relatively small susceptibility change. For EIT based on simultaneous electric resonance and magnetic resonance, not only incident electric field but also the incident magnetic field pays a role on the susceptibility of system. The influence of the incident magnetic field leads to relatively smaller susceptibility change compared with that based on electric resonance near field coupling to magnetic resonance.

Plasmon-induced transparency in coupled triangle-rod arrays

We demonstrate polarization-dependent plasmon-induced transparency in coupled triangle-rod arrays. The observed phenomenon is the result of the destructive interference between the bright and dark resonators in this coupled system, which is verified through the numerical simulations using the finite-difference time-domain (FDTD) method. By precisely controlling the structural parameters of the coupled triangle-rod system, the plasmon-induced transparency can be effectively manipulated. This plasmonically coupled nanostructure could be potentially useful for designing and developing artificial plasmonic molecules and metamaterials with desired functions, which may further find promising applications in biosensing, nanoparticle trapping and optical filters.

Plasmonic nanoclocks

Plasmonic spectra of "nanoclock" metamaterials can be topologically mapped on a torus. We manufactured arrays of such a metamaterial with different "time" shown on the clocks and demonstrated that the near-infrared spectra of the nanostructures can be predictably tuned exhibiting a rich series of high-order plasmon modes, from the electric dipole to exotic electric triakontadipole that could be engaged in chemo/biosensor applications.

Plasmonic Fano resonances in metallic nanorod complexes

Plasmonic Fano resonances (FRs) in nanostructures have been extensively studied in recent years. Nanorod-based complexes for FRs have also attracted much attention. The basic optical properties and fabrication technology of different kinds of plasmonic nanorods have been greatly developed over the last several years. The mutipole plasmon resonances and their flexible adjustment ranges on nanorods make them promising for FR modifications and structure diversity. In this paper, we review some recently studied plasmonic nanorod based nanostructures for FRs, including single nanorods, dimers, mutipole rods and nanorod-nanoparticle hybrids. The corresponding applications of the FRs are also briefly discussed.

Metal nanoparticle plasmons operating within a quantum lifetime

We investigate the dynamics of a plasmonic oscillation over a metal nanoparticle when it is strongly coupled to a quantum emitter (e.g. quantum dot, molecule). We simulate the density matrix evolution for a simple model, a coupled classical-quantum oscillators system. We show that the lifetime of the plasmonic oscillations can be increased several orders of magnitude, up to the decay time of the quantum emitter. This effect shows itself as the narrowing of the plasmon emission band in the spaser (surface plasmon amplification by the stimulated emission of radiation) experiment [Nature, 2009, 460, 1110], where a gold nanoparticle interacts with the surrounding molecules. Enhancement of the plasmonic excitation lifetime enables stimulated emission to overcome the spontaneous one. The enhancement occurs due to the emergence of a phenomenon analogous to electromagnetically induced transparency (EIT). The effect can find applications in many areas of nanoscale physics, such as in quantum information with plasmons and in increasing solar cell efficiency.

Polarization and incidence insensitive dielectric electromagnetically induced transparency metamaterial

In this manuscript, we demonstrate numerically classical analogy of electromagnetically induced transparency (EIT) with a windmill type metamaterial consisting of two dumbbell dielectric resonator. With proper external excitation, dielectric resonators serve as EIT bright and dark elements via electric and magnetic Mie resonances, respectively. Rigorous numerical analyses reveal that dielectric metamaterial exhibits sharp transparency peak characterized by large group index due to the destructive interference between EIT bright and dark resonators. Furthermore, such EIT transmission behavior keeps stable property with respect to polarization and incidence angles.

Multispectral plasmon-induced transparency in triangle and nanorod(s) hybrid nanostructures

We theoretically investigate the optical properties of a hybrid nanostructure consisting of one triangle and one nanorod. A plasmon-induced transparency (PIT) resonance appears in the transmission spectrum, which is ascribed to the induced multipole plasmon mode of the nanorod. Multispectral PIT resonances are observed, when two or more nanorods are put in proximity to the triangle. It is proved that the combined effects of the induced multipole plasmon mode of nanorods and the cavity resonant mode contribute to these PIT peaks. The tunability of PIT on the geometrical parameters is also presented.

Control of Fano asymmetry in plasmon induced transparency and its application to plasmonic waveguide modulator

In this paper, we derive a governing equation for spectral asymmetry in electromagnetically induced transparency (EIT). From the key parameters of asymmetry factor - namely dark mode quality factor Q(d), and frequency separation between bright and dark mode Δω(bd) = (ω(b) - ω(d)) -, a logical pathway for the maximization of EIT asymmetry is identified. By taking the plasmonic metal-insulator-metal (MIM) waveguide as a platform, a plasmon-induced transparency (PIT) structure of tunable frequency separation Δω(bd) and dark mode quality factor Q(d) is suggested and analyzed. Compared to previous works on MIM-based plasmon modulators, an order of increase in the performance Fig. (12dB contrast at ~60% throughput) was achieved from the highly asymmetric, narrowband PIT spectra.