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Register a new userGeneration and Tunability of Supermodes in Tamm Plasmon Topological Superlattices
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In this study, we propose and experimentally demonstrate a novel kind of Tamm plasmon topological superlattice (TTS) by engineering Tamm photonic crystals (TPCs) belonging to a different class of topology. Utilizing specifically designed double-layer metasurfaces etching on planar multilayered photonic structures, the TPC that supports the Tamm plasmon photonic bandgap is realized in the visible regime. Through the coupling of topological interface states existing between different TPCs, hybrid topological interface states of Tamm plasmon, called supermodes, are obtained that can be fully described by a tight-binding model. Meanwhile, we can achieve a tunable bandwidth of supermodes via varying the etching depth difference between double-layer metasurfaces. We show that the bandwidth decreases with the increase of etching depth difference, resulting in a nearly flat dispersion of supermodes with strong localization regardless of excitation angles. All the results are experimentally verified by measuring angular-resolved reflectance spectra. The TTS and supermodes proposed here open a new pathway for the manipulation of Tamm plasmons, based on which various promising applications such as integrated photonic devices, optical sensing, and enhancing light-matter interactions can be realized.
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We report for the first time the bandgap engineering of Tamm plasmon photonic crystals - Tamm plasmon structures of which the metalic layer is periodically patterned into lattice of subwavelength period. By adopting a double period design, we evidenced experimentally a complete photonic bandgap up to $150,nm$ in the telecom range. Moreover, such design offers a great flexibility to tailor on-demand, and independently, the band-gap size from $30,nm$ to $150,nm$ and its spectral position within $50,nm$. Finally, by implementing a defect cavity within the Tamm plasmon photonic crystal, an ultimate cavity of $1.6mu m$ supporting a single highly confined Tamm mode is experimentally demonstrated. All experimental results are in perfect agreement with numerical calculations. Our results suggests the possibility to engineer novel band dispersion with surface modes of hybrid metalic/dielectric structures, thus open the way to Tamm plasmon towards applications in topological photonics, metamaterials and parity symmetry physics.
We have theoretically demonstrated Rabi-like splitting and self-referenced refractive index sensing in hybrid plasmonic-1D photonic crystal structures. The coupling between Tamm plasmon and cavity photon modes are tuned by incorporating a low refractive index spacer layer close to the metallic layer to form their hybrid modes. Anticrossing observed in the dispersion validates the strong coupling between the modes and causes Rabi-like splitting, which is supported by coupled mode theory. The Rabi-like splitting energy decreases with increasing number of periods (N) and refractive index contrast ({eta}) of the two dielectric materials used to make the 1D photonic crystals, and the observed variation is explained by an analytical model. The angular and polarization dependency of the hybrid modes shows that the polarization splitting of the lower hybrid mode is much stronger than that of the upper hybrid mode. Further investigating the hybrid modes, it is seen that one of the hybrid modes remains unchanged while other mode undergoes significant change with varying the cavity medium, which makes it useful for designing self-referenced refractive index sensors for sensing different analytes. For {eta}=1.333 and N=10 in a hybrid structure, the sensitivity increases from 51 nm/RIU to 201 nm/RIU with increasing cavity thickness from 170 nm to 892 nm. For a fixed cavity thickness of 892 nm, the sensitivity increases from 201 nm/RIU to 259 nm/RIU by increasing {eta} from 1.333 to 1.605. The sensing parameters such as detection accuracy, quality factor, and figure of merit for two different hybrid structures ([{eta}=1.333, N=10] and [{eta}=1.605, N=6]) are evaluated and compared. The value of resonant reflectivity of one of the hybrid modes changes considerably with varying analyte medium which can also be used for refractive index sensing.
We demonstrate theoretically the existence of one-way Tamm plasmon-polaritons on the interface between magnetophotonic crystals and conducting metal oxides. In contrast to conventional surface plasmon-polaritons (SPPs), Tamm plasmon-polariton (TPPs) occur at frequencies above the bulk plasma frequency of the conducting materials, provided that the dispersion curves of such surface modes lie outside the light cone for the conducting oxides and simultaneously fall into the photonic band gap of the magnetophotonic crystal. The nonreciprocal properties of TPPs are caused by violation of the periodicity and time reversal symmetry in the structure. Calculations on the field distribution and transmission spectra through the structure are employed to confirm the theoretical results, which could potentially impact on a broad range of SPP-related phenomena in applications.
We present a semi-analytical formulation for calculating the supermodes and corresponding Bloch factors of light in hexagonal lattice photonic crystal waveguide arrays. We then use this formulation to easily calculate dispersion curves and predict propagation in systems too large to calculate using standard numerical methods.
Quadrupole topological insulator is a symmetry-protected higher-order topological phase with intriguing topology of Wannier bands, which, however, has not yet been realized in plasmonic metamaterials. Here, we propose a lattice of plasmon-polaritonic nanocavities which can realize quadrupole topological insulators by exploiting the geometry-dependent sign-reversal of the couplings between the daisy-like nanocavities. The designed system exhibits various topological and trivial phases as characterized by the nested Wannier bands and the topological quadrupole moment which can be controlled by the distances between the nanocavities. Our study opens a pathway toward plasmonic topological metamaterials with quadrupole topology.
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