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SHG in plasmonic structures


Plasmonic solitons


Anderson localization


Quantum plasmonics



Second-Harmonic Generation in Ensembles of Metallic Nanowires
One of the most important properties of plasmonic nanostructures is the strong optical near-field enhancement induced by the interaction with electromagnetic waves, an effect that is usually a consequence of the resonant excitation of surface-plasmon polaritons. As a result, one can induce strong nonlinear optical effects at a moderate optical power. In this context, we have recently developed a comprehensive theoretical description based on the multiple-scattering matrix formalism of the second harmonic generation (SHG) in metamaterials consisting of arbitrary distributions of cylindrical nanowires made of centrosymmetric materials, such as metals. Our theory allows one to calculate the electromagnetic field at both the fundamental frequency and second harmonic, as well as the total cross section, the absorption cross section, and the scattering cross section. In particular, our formalism fully describes the nonlinear optical response of the metamaterial by incorporating the contributions of both the surface and bulk nonlinear polarizations and can be applied to both s- and p-polarized incident waves. We have used this theoretical method and its numerical implementation to investigate the SHG in a series of particular cases of practical interest, namely, a single metallic cylinder, chains of metallic cylinders, periodic and random distributions of such cylinders, and plasmonic cavities. In particular, we have studied the relation between the local field enhancement, via the excitation of surface plasmon-polariton modes, and the amount of energy absorbed or scattered in the far-field, at the fundamental frequency and second harmonic. As a possible technological application of these ideas, we have investigated the feasibility of using nonlinear modes of plasmonic cavities to design ultra-compact plasmonic sensors with enhanced sensitivity. More information about this topic can be found here.

Relevant publications:
  • C. G. Biris and N. C. Panoiu, Second Harmonic Generation in Metamaterials based on Homogeneous Centrosymmetric Nanowires, Phys. Rev. B 81, 195102 (2010) (also selected by the editors of Phys. Rev. B to be an Editors' Suggestion). [pdf]
  • C. G. Biris and N. C. Panoiu, Nonlinear pulsed excitation of high-Q optical modes of plasmonic cavities made of metallic nanowires, Opt. Express 18, 17165 (2010) (also featured in the Virtual Journal of Ultrafast Science 9 (10), October, 2010). [pdf]
  • C. G. Biris and N. C. Panoiu, Excitation of dark plasmonic cavity modes via nonlinearly induced dipoles: applications to near-infrared plasmonic sensing, Nanotechnology 22, 235502 (2011). [pdf]
  • C. G. Biris and N. C. Panoiu, Excitation of Linear and Nonlinear Cavity Modes upon Interaction of Femtosecond Pulses with Arrays of Metallic Nanowires, Appl. Phys. A: Materials Science & Processing 103, 863 (2011). [pdf]
  • C. G. Biris and N. C. Panoiu, Nonlinear Surface-Plasmon Whispering-Gallery Modes in Metallic Nanowire Cavities, Phys. Rev. Lett. 111, 203903 (2013). [pdf]


Plasmonic Solitons and Vortices in Arrays of Metallic Nanowires
Recently we predicted theoretically that stable subwavelength plasmonic lattice solitons are formed in arrays of metallic nanowires embedded in a nonlinear optical medium. More specifically, in this project, which is a collaboration with Dr. Fangwei Ye from the Physics Department of Shanghai Jiao Tong University, we have demonstrated that the tight confinement of the guiding modes of the metallic nanowires, combined with the strong optical nonlinearity induced by the enhanced field at the metal surface, provide the main physical mechanisms for balancing the wave diffraction and the formation of plasmonic lattice solitons (see the left panels below). As the conditions required for the formation of plasmonic lattice solitons are satisfied in a variety of plasmonic systems, we expect these nonlinear modes to have important applications to subwavelength nanophotonics. In particular, we demonstrated that the subwavelength plasmonic lattice solitons can be used to optically manipulate with nanometer accuracy the power flow in ultracompact photonic systems. In addition, we have shown that 2D plasmonic arrays support more complex nonlinear modes, namely stable optical vortices, which perhaps represents the first example of subwavelength vortex solitons (see the right panels below).

Relevant publications:
  • F. Ye, D. Mihalache, B. Hu, and N. C. Panoiu, Subwavelength Plasmonic Lattice Solitons in Arrays of Metallic Nanowires, Phys. Rev. Lett. 104, 106802 (2010) (also featured in the Virtual Journal of Nanoscale Science and Technology 21 (12), March 22, 2010). [pdf]
  • F. Ye, D. Mihalache, B. Hu, and N. C. Panoiu, Subwavelength vortical plasmonic lattice solitons, Opt. Lett. 36, 1179 (2011) (also featured in the Virtual Journal of Nanoscale Science and Technology 23 (16), April 25, 2011). [pdf]
  • F. Ye, D. Mihalache, and N. C. Panoiu, Sub-wavelength Plasmonic Solitons in 1D and 2D Arrays of Coupled Metallic Nanowires, in Spontaneous Symmetry Breaking, Self-Trapping, and Josephson Oscillations, Ed. B. A. Malomed (Progress in Optical Science and Photonics, Vol. 1, Springer, Berlin, Germany, 2013). [pdf]


Anderson Localization in Arrays of Plasmonic Nanowires
Using a generic example of a disordered plasmonic system, namely an array of coupled, randomly perturbed metallic nanowires, we have recently demonstrated that structural disorder can induce light localization at deep-subwavelength scale in plasmonic nanostructures. Our theoretical and computational analysis is based on solving the complete set of three-dimensional Maxwell equations and thus it provides a rigorous description of the dynamics of the plasmonic field at the nanoscale. We have found that a random variation of the radius of coupled plasmonic nanowires leads to the Anderson localization of the collective excitation of surface-plasmon polaritons, the characteristic localization length of these disorder-induced optical modes being significantly smaller than the wavelength. Remarkably, our analysis shows that the optical gain coefficient needed to compensate the optical losses in the plasmonic components of the system is much smaller than the loss coefficient of the metal, a finding that can be extremely relevant for experimental investigations of Anderson localization in plasmonic nanostructures. The excitation and propagation of Anderson localized surface-plasmon polaritons have also been addressed. This work is a collaboration with Dr. Fangwei Ye from the Physics Department of Shanghai Jiao Tong University and Prof. Boris Malomed from the School of Electrical Engineering of Tel Aviv University.

Relevant publications:
  • X. Shi, F. Ye, X. Chen, B. A. Malomed, and N. C. Panoiu, Anderson localization at the subwavelength scale for surface plasmon polaritons in disordered arrays of metallic nanowires, Phys. Rev. B 89, 195428 (2014). [pdf]
  • H. Deng, X. Chen, B. A. Malomed, N. C. Panoiu, and F. Ye, Transverse Anderson localization of light near Dirac points of photonic nanostructures, Sci. Rep. 5, 15585 (2015). [pdf]
  • H. Deng, X. Chen, B. A. Malomed, N. C. Panoiu, and Fangwei Ye, Tunability and Robustness of Dirac Points of Photonic Nanostructures (invited), IEEE J. Sel. Topics Quantum Electron. 22, 5000509 (2016). [pdf]


Quantum Interaction between Molecules and Plasmonic Metamolecules
Recently there has been an increasing interest in the physics of light matter interaction at the nanoscale. In particular, quantum plasmonics is emerging as an ideal field where such new ideas and phenomena can be studied, primarily because plasmonic nanostructures facilitate an enhanced coupling between light and matter. In this context, we have proposed a quantum mechanical model that fully describes the interaction between molecules and plasmonic metamolecules (plasmonic structures that have a series of optical resonances). More specifically, in collaboration with Dr. Paul Warburton's group at the London Centre for Nanotechnology, we have demonstrated that the coupling between tunable broadband modes of an array of plasmonic metamolecules and a vibrational mode of carbonyl bond of poly(methyl methacrylate) produces a Fano-like resonance, which can be tuned in situ by varying the polarization of the incident light. The interaction between the plasmon modes and the molecular resonance was investigated using both rigorous electromagnetic calculations and a quantum mechanical model describing the quantum interference between a discrete state (the vibrational mode of the molecule) and two continua (the broad plasmon resonances). The predictions of the quantum mechanical model were in good agreement with the experimental data and provided an intuitive interpretation, at the quantum level, of the plasmon molecule coupling.

Relevant publications: E. J. Osley, C. G. Biris, P. G. Thompson, R. R. F. Jahromi, P. A. Warburton, and N. C. Panoiu, Fano Resonance Resulting from a Tunable Interaction between Molecular Vibrational Modes and a Double Continuum of a Plasmonic Metamolecule, Phys. Rev. Lett. 110, 087402 (2013). [pdf]