Arthur R. Davoyan

Nonlinear plasmonic slot waveguides

We study nonlinear modes in a subwavelength slot waveguide created by a nonlinear dielectric slab sandwiched between two metals. We present the dispersion diagrams of the families of nonlinear guided modes and reveal that the symmetric mode undergoes the symmetry-breaking bifurcation and becomes primarily localized near one of the interfaces. We also find that the antisymmetric mode may split into two brunches giving birth to two families of nonlinear antisymmetric modes.

Self-focusing and spatial plasmon-polariton solitons

We study nonlinear propagation of surface plasmon polaritons along an interface between metal and nonlinear Kerr dielectric. We demonstrate numerically self-focusing of a plasmon beam at large powers and the formation of slowly decaying spatial soliton in the presence of losses. We develop an analytical model for describing the evolution of spatial plasmon-solitons and observe a good agreement with numerical results.

All-passive nonreciprocal metastructure.

One-way propagation of light, analogous to the directional flow of electrons in the presence of electric potential difference, has been an important goal in the wave–matter interaction. Breaking time-reversal symmetry in photonic flows is faced with challenges different from those for electron flows. In recent years several approaches and methods have been offered towards achieving this goal. Here we investigate another systematic approach to design all-passive relatively high-throughput metastructures that exhibit nonreciprocal properties and achieve wave-flow isolation. Moreover, we build on those findings and propose a paradigm for a quasi-two-dimensional metastructure that mimics the nonreciprocal property of Faraday rotation without using any magnetic or electric biasing. We envision that the proposed approaches may serve as a building block for all-passive time-reversal symmetry breaking with potential applications for future nonreciprocal systems and devices

One-way phonon isolation in acoustic waveguides

We present a method to achieve one-way phonon isolation in acoustic waveguides by considering spatio-temporal modulation of material properties. One-way conversion between symmetric and antisymmetric shear horizontal modes of an unbounded plate acoustic waveguide is numerically demonstrated using this method. Analytical and numerical evidence for the possibility of mode conversion is presented. Possible experimental implementation and applications for on-chip signal isolation in MEMS devices are also suggested.

Optical isolation with epsilon-near-zero metamaterials

We suggest a principle for isolation of circularly polarized waves in magnetically active extreme-parameter metamaterials. Using theoretical analysis and numerical simulations, we show that metamaterials with extreme parameters, such as epsilon-near-zero materials (ENZ), when merged with magneto-optical materials, become transparent for forward circularly polarized waves of a given handedness and opaque for backward propagating waves of the same handedness. We theoretically study two possible implementations of such hybrid materials: (1) the case of metal-dielectric stacks; and (2) rectangular waveguide near its cut-off frequency. We prove that these structures can be utilized as compact isolators for circularly polarized waves.

Backward and forward modes guided by metal-dielectric-metal plasmonic waveguides

We revisited the problem of the existence of plasmonic modes guided by metal- dielectric-metal slot waveguides. For the case of lossless slot waveguides, we classify the guided modes in the structure with the metal dispersion and found that, in a certain parameter range, three different guided modes coexist at a fixed frequency, two (symmetric and antisymmetric) forward propagating modes and the third, backward propagating antisymmetric mode. We study the properties of the forward and backward plasmonic guided modes in the presence of realistic losses, and discuss the importance of evanescent modes in lossy structures.

Nanoscale plasmonic circulator

Breaking time reversal symmetry of the light flow, implying optical wave isolation and directional light guiding, is crucial for signal handling and integrated optics. Such signal isolation is possible with an optical circulator—a three-port magneto-active nonreciprocal device, which transmits light from any of its input ports into the next port in a circular order, isolating the remaining port. Small magneto-optical activity at optical frequencies challenges the miniaturization and further on-chip integration of this key fundamental component. Here we demonstrate theoretically that by employing principles of plasmonic mode engineering it is possible to enhance significantly magneto-optical response in a deep subwavelength regime and suggest a conceptual approach for a design of an ultracompact nanoscale passive optical circulator. This work paves the way for future generation of nonreciprocal integrated optics with a nanoscale on-chip compatibility.

Enhanced emission and light control with tapered plasmonic nanoantennas

We introduce a design of Yagi-Uda plasmonic nanoantennas for enhancing the directive gain and achieving control over the angular emission of light. We demonstrate that tapering of nanoantenna elements allows to decrease the inter-element spacing tenfold also enhancing the emission directivity. We find the optimal tapering angle that provides the maximum directivity enhancement and the minimum end-fire beamwidth.

Graphene surface emitting terahertz laser: Diffusion pumping concept

We suggest a concept of a tunable graphene-based terahertz (THz) surface emitting laser with diffusion pumping. We employ significant difference in the electronic energy gap of graphene and a typical wide-gap semiconductor, and demonstrate that carriers generated in the semiconductor can be efficiently captured by graphene resulting in population inversion and corresponding THz lasing from graphene. We develop design principles for such a laser and estimate its performance. We predict up to 50 W/cm2 terahertz power output for 100 kW/cm2 pump power at frequency around 10 THz at room temperature.

Multifrequency tapered plasmonic nanoantennas

Abstract We suggest a multifrequency Yagi–Uda-type nanoantenna loaded with an array of tapered plasmonic nanorods. The arrays of director nanorods can be used for the excitation of the nanoantenna by emitters matched spectrally with their resonant frequency and placed in their near-field region. An overlap of multifrequency operating bands of the nanoantenna provides novel opportunities for broadband operation, and the same nanoantenna architecture can be employed both as a transmitter and/or as a receiver, thus being useful for broadband wireless communication.