D.H. Werner

Park University, Parkville, Missouri, United States

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Publications (468)556.81 Total impact

  • Anastasios H. Panaretos, Douglas H. Werner
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    ABSTRACT: In this paper we theoretically investigate the feasibility of creating a dual-mode plasmonic nanorod antenna. The proposed design methodology relies on adapting to optical wavelengths the principles of operation of trapped dipole antennas, which have been widely used in the low MHz frequency range. This type of antenna typically employs parallel LC circuits, also referred to as “traps”, which are connected along the two arms of the dipole. By judiciously choosing the resonant frequency of these traps, as well as their position along the arms of the dipole, it is feasible to excite the λ/2 resonance of both the original dipole as well as the shorter section defined by the length of wire between the two traps. This effectively enables the dipole antenna to have a dual-mode of operation. Our analysis reveals that the implementation of this concept at the nanoscale requires that two cylindrical pockets (i.e. loading volumes) be introduced along the length of the nanoantenna, inside which plasmonic core-shell particles are embedded. By properly selecting the geometry and constitution of the core-shell particle as well as the constitution of the host material of the two loading volumes and their position along the nanorod, the equivalent effect of a resonant parallel LC circuit can be realized. This effectively enables a dual-mode operation of the nanorod antenna. The proposed methodology introduces a compact approach for the realization of dual-mode optical sensors while at the same time it clearly illustrates the inherent tuning capabilities that core-shell particles can offer in a practical framework.
    Optics Express 04/2015; 23(7). DOI:10.1364/OE.23.008298 · 3.53 Impact Factor
  • Anastasios H. Panaretos, Douglas H. Werner
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    ABSTRACT: In this paper we demonstrate the feasibility of using multiport network theory to describe the admittance properties of a longitudinally loaded plasmonic nanorod antenna. Our analysis reveals that if the appropriate terminal ports are defined across the nanorod geometry then the corresponding voltage and current quantities can be probed and thus it becomes feasible to extract the admittance matrix of the structure. Furthermore, it is demonstrated that by utilizing cylindrical dielectric waveguide theory, closed form expressions can be derived that uniquely characterize the loading material in terms of its admittance. The combination of the admittance matrix information along with the load admittance expressions provides an effective methodology for computing the nanorod’s input admittance/impedance for arbitrary loading scenarios. This is important because the admittance resonances are associated with the structure’s scattering peaks which are excited by a plane wave polarized parallel to its long dimension. Subsequently, the proposed approach provides a fast and computationally efficient circuit-based methodology to predict and custom engineer the scattering properties of a loaded plasmonic nanorod without having to rely on repetitive lengthy full wave simulations.
    Optics Express 02/2015; 23(4). DOI:10.1364/OE.23.004459 · 3.53 Impact Factor
  • Micah D. Gregory, Douglas H. Werner
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    ABSTRACT: The recently popularized memristor, short for memory resistor, is investigated in this paper for its potential as a new and attractive method for enabling reconfigurable radio-frequency (RF) devices. The charge- or flux-controlled resistance of this “fourth circuit element” allows for easy reconfigurability and maintains its configured state in the absence of controlling signals. A specialized finite-difference time-domain simulation code is developed and employed to design devices with embedded memristors. The time-domain code allows observation of the nonlinear memristor switching characteristics and real-time functionality of the reconfigurable device. Several different reconfigurable RF devices are designed here to demonstrate the versatility of the memristor and determine the behavior of systems which utilize them.
    IEEE Antennas and Propagation Magazine 02/2015; 57(1):239-248. DOI:10.1109/MAP.2015.2397153 · 1.15 Impact Factor
  • IEEE Antennas and Wireless Propagation Letters 01/2015; DOI:10.1109/LAWP.2015.2390145 · 1.95 Impact Factor
  • P. E. Sieber, D. H. Werner
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    ABSTRACT: In this work a new technique for synthesizing metamaterials using Bézier surfaces is introduced. First, the computational efficiency for the optimization of a reconfigurable Bézier quarter-wave plate metasurface is compared to the popular technique of optimizing pixelized surfaces via a binary Genetic Algorithm (GA). For the presented design methodology, a real valued optimization technique is employed which is based on the Covariance Matrix Adaptation Evolutionary Strategy (CMA-ES). When compared to the GA, the optimizations of Bézier surfaces using CMA-ES are shown to consistently arrive at better solutions with an order of magnitude reduction in the required number of function evaluations. Additionally, more examples of Bézier metasurfaces are presented in the form of broadband quarter-wave and half-wave plate designs operating at optical wavelengths, subsequently exhibiting bandwidths which outperform metasurface designs found in the current literature.
    Optics Express 12/2014; 22(26). DOI:10.1364/OE.22.032371 · 3.53 Impact Factor
  • Source
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    ABSTRACT: Quasi two-dimensional metasurfaces composed of subwavelength nanoresonator arrays can dramatically alter the properties of light in an ultra-thin planar geometry, enabling new optical functions such as anomalous reflection and refraction, polarization filtering, and wavefront modulation. However, previous metasurface-based nanostructures suffer from low efficiency, narrow bandwidth and/or limited field-of-view due to their operation near the plasmonic resonance. Here we demonstrate plasmonic metasurface-based nanostructures for high-efficiency, angle-insensitive polarization transformation over a broad octave-spanning bandwidth. The structures are realized by optimizing the anisotropic response of an array of strongly coupled nanorod resonators to tailor the interference of light at the subwavelength scale. Nanofabricated reflective half-wave and quarter-wave plates designed using this approach have measured polarization conversion ratios and reflection magnitudes greater than 92% over a broad wavelength range from 640 to 1290 nm and a wide field-of-view up to ±40°. This work outlines a versatile strategy to create metasurface-based photonics with diverse optical functionalities.
    Scientific Reports 12/2014; 4:7511. DOI:10.1038/srep07511 · 5.08 Impact Factor
  • Zhi Hao Jiang, Douglas H. Werner
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    ABSTRACT: Low-profile and light-weight coatings that offer comprehensive manipulation of the electromagnetic scattering for finite-length objects are highly desirable, but not yet achieved, for applications including camouflaging, deceptive sensing, radar cognition control, and defense security. Here, for the first time, the theory, practical design, and experimental demonstration of quasi-three-dimensional and angle-tolerant electromagnetic illusion coatings are presented which have been enabled by ultrathin single-layer functional metasurfaces. By controlling the multiple Mie scattering coefficients using the tangential and non-vanishing radial electromagnetic responses of the metasurface, the quasi-two-dimensional coating transforms the electromagnetic perception of one object to mimic that of another which has been pre-selected by the designer. The illusion coating, which is homogeneous but anisotropic, is realized using hundreds of composite electric and magnetic sub-wavelength unit cells operating at frequencies away from their resonance. Two different prototypes of the metasurface illusion coatings were fabricated and characterized, demonstrating very good camouflaging performance for finite-length dielectric as well as conducting objects within a field-of-view up to ±10° off normal. This work paves the way for practical artificially engineered material coatings with exotic and versatile scattering control capabilities that would enable a wide range of applications throughout the entire electromagnetic spectrum.
    Advanced Functional Materials 12/2014; 24(48). DOI:10.1002/adfm.201401561 · 10.44 Impact Factor
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    ABSTRACT: A method is presented that allows for the efficient design of capacitively loaded finite-size electromagnetic bandgap (EBG) structures, which can target a wide range of design objectives. The design flexibility is achieved by adding arbitrary nonuniform capacitive loading to an underlying periodic EBG structure. This system can be interpreted as having an effective aperiodic structure, which allows more design flexibility in terms of bandgap engineering. To choose the proper capacitances, a powerful global optimization technique known as the covariance matrix adaptation evolutionary strategy is employed that is aided by a fast port-reduction strategy. This approach avoids the need to carry out multiple computationally expensive full-wave simulations during the course of the optimization process by requiring only a single full-wave simulation be performed prior to initiating the optimization. To demonstrate the utility of this method, the capacitive loading of a mushroom-type EBG structure in a parallel-plate waveguide is optimized to reduce transmission from 2.4 to 7 GHz. This design was fabricated and the measured response was found to be in good agreement with the simulations. Using the same initial full-wave simulation, another structure was designed to improve isolation at the 2.4-, 3.6-, and 5-GHz WLAN bands to below $-{hbox{22}}$ dB. An additional set of structures are also designed using capacitively loaded mushroom-type EBG surfaces without placing them inside of a parallel-plate waveguide.
    IEEE Transactions on Microwave Theory and Techniques 09/2014; 62(9):1962-1972. DOI:10.1109/TMTT.2014.2335175 · 2.94 Impact Factor
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    ABSTRACT: We propose a compact conformal wearable antenna that operates in the 2.36–2.4 GHz medical body-area network band. The antenna is enabled by placing a highly truncated metasurface, consisting of only a two by two array of I-shaped elements, underneath a planar monopole. In contrast to previously reported artificial magnetic conducting ground plane backed antenna designs, here the metasurface acts not only as a ground plane for isolation, but also as the main radiator. An antenna prototype was fabricated and tested, showing a strong agreement between simulation and measurement. Comparing to previously proposed wearable antennas, the demonstrated antenna has a compact form factor of $0.5 lambda _{0} times 0.3 lambda _{0} times 0.028 lambda _{0}$, all while achieving a 5.5% impedance bandwidth, a gain of 6.2 dBi, and a front-to-back ratio higher than 23 dB. Further numerical and experimental investigations reveal that the performance of the antenna is extraordinarily robust to both structural deformation and human body loading, far superior to both planar monopoles and microstrip patch antennas. Additionally, the introduced metal backed metasurface enables a 95.3% reduction in the specific absorption rate, making such an antenna a prime candidate for incorporation into various wearable devices.
    IEEE Transactions on Antennas and Propagation 08/2014; 62(8):4021-4030. DOI:10.1109/TAP.2014.2327650 · 2.46 Impact Factor
  • Xiande Wang, D.H. Werner, J.P. Turpin
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    ABSTRACT: An efficient methodology is introduced for rapid analysis and design of three-dimensional (3-D) doubly periodic structures over a wide frequency range based on hybrid finite element boundary integral (FEBI) methods. The 3-D doubly periodic structures can be represented as nonorthogonal lattices composed of general inhomogeneous bianisotropic media with arbitrarily-shaped metallic patches. Based on Floquet theory and periodic boundary conditions, the original stated problem that involves infinite periodic structures can be converted into a single unit cell. Using the equivalence principle, the derived BI equation formulation is applied to the top and bottom surfaces of the unit cell, which results in a perfectly reflectionless boundary condition for the FE-based approach. Then, the unit cell was meshed using triangular prismatic volume elements, which provide a great deal of flexibility in modeling complex planar geometries with arbitrary shapes in the transverse direction. The adaptive integral method (AIM) was employed to accelerate the calculation of the matrix-vector product for the BI portion within the iterative solver. Furthermore, a model-based parameter estimation (MBPE) technique was proposed for the wide-band interpolation of the required impedance matrix elements in the BI part for near field components that were used in the AIM procedure. The accuracy and efficiency of the proposed hybrid algorithms are demonstrated by the presented numerical results (e.g., in comparison with analytical solutions). Several simulation results are presented to illustrate the flexibility of the proposed methods for analysis of frequency selective surfaces with arbitrarily-shaped metallic patches, bianisotropic materials, and nonorthogonal lattice configurations.
    IEEE Transactions on Antennas and Propagation 08/2014; 62(8):4067-4080. DOI:10.1109/TAP.2014.2322903 · 2.46 Impact Factor
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    ABSTRACT: The use of inhomogeneous metamaterial lenses is proposed to enable suitable radiation properties for arbitrary-shape antenna arrays. Towards this end, the Quasi-Conformal Transformation Optics (QCTO) methodology is generalized to allow an arbitrary physical arrangement coated with a suitable lens to exhibit the same radiating features of an arbitrary reference virtual array in free space. A representative numerical example, concerned with a two-dimensional layout, is presented to assess the effectiveness of the proposed method as well as the enhanced features of the resulting metamaterial-coated arrays with respect to standard conformal arrangements.
    IEEE Transactions on Antennas and Propagation 08/2014; 62(8):4089-4095. DOI:10.1109/TAP.2014.2327643 · 2.46 Impact Factor
  • Anastasios H. Panaretos, Douglas H. Werner
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    ABSTRACT: The scattering and transparency properties of layered plasmonic nanoparticles are studied from the perspective of spherical transmission line theory. The advantage of this approach is that the interaction of the nanoparticle with its surroundings can be very conveniently represented as a combination of admittances. In this framework we reformulate the total impedance expression of a spherical nanoparticle, and from this we derive through a compact and intuitive methodology the two conditions that govern the resonance and transparency states of a nanoparticle. These conditions are satisfied when the particle’s input admittance becomes inductive and capacitive, respectively. The recursive relations that determine the TM admittance of an electrically small, radially inhomogeneous dielectric sphere are analyzed, and it is demonstrated that any degree of layering can be homogenized by a decomposition into successive binary mixtures. The appropriate material choice results in mixtures that exhibit multiple Lorentzian resonances that are directly mapped to the particle’s admittance, due to its small electrical size. Consequently, the particle’s admittance exhibits multiple inductive-to-capacitive switchings, and thus the resonance and transparency conditions are satisfied at multiple frequencies. This explains the well-known feature of multiple resonance–transparency pairs observed in the scattering signature of layered plasmonic nanoparticles.
    Journal of the Optical Society of America B 07/2014; 31(7). DOI:10.1364/JOSAB.31.001573 · 1.81 Impact Factor
  • Xiande Wang, D.H. Werner, J.P. Turpin
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    ABSTRACT: A sub-entire domain (SED) basis function method, which was first introduced for modeling large-scale finite periodic PEC structures in free space, has been extended for fast characterization of electromagnetic scattering from an electrically large planar finite periodic microstrip patch array. The microstrip array may have a nonrectangular layout and non-orthogonal lattice configurations (e.g., hexagons or quadrangles). Based on the mixed potential integral equation, and utilizing the proposed SED basis function algorithm, the original large-scale finite periodic array of microstrip patches can be efficiently simulated by decomposing it into two problems with matrix equations of small dimensions. The first is to construct the SED basis functions for the corresponding microstrip arrays with orthogonal/non-orthogonal lattices. Three kinds of the SED basis functions are constructed, including those related to the edge patch elements, the interior patch elements, and the corner patch elements. The second is to solve the system equation with significantly reduced problem dimension as compared to the original larger problem. Based on the obtained SED basis functions, the reduced matrix equation of small size can be generated by the Galerkin procedure, and solved by use of the LU (lower-upper) decomposition-based direct solver, which results in a fast solution. The accuracy and efficiency of the developed algorithms are demonstrated by numerical tests that include the scattering from several large-scale finite periodic arrays of microstrip patches with rectangular, non-orthogonal lattices.
    IEEE Transactions on Antennas and Propagation 05/2014; 62(5):2543-2552. DOI:10.1109/TAP.2014.2309116 · 2.46 Impact Factor
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    ABSTRACT: A high-gain reduced-profile antenna is designed by combining the effects of a near-zero-index volumetric metamaterial lens and an artificial magnetic conducting (AMC) ground plane. The AMC/metalens antenna design presented here has 20% reduced height over an equivalent metalens antenna with conventional metallic ground plane at the cost of reduced peak directivity and pattern bandwidth. Both the metamaterial unit cells and the mushroom-type AMC structure are designed independently and retuned in the presence of the other for optimal performance. The lens collimates the electromagnetic radiation of a dipole feed by refraction as well as via a Fabry-Perot cavity effect, with resulting gain and patterns that are better than either mechanism can achieve individually. Full wave simulations of the entire metamaterial and AMC structure with a feed dipole agree well with measurements of the fabricated design.
    IEEE Transactions on Antennas and Propagation 03/2014; 62(4). DOI:10.1109/TAP.2014.2302845 · 2.46 Impact Factor
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    ABSTRACT: A low-profile high-gain unidirectional antenna is proposed and demonstrated using both metamaterial (MM) and substrate-integrated waveguide (SIW) technologies. First, the leaky modes supported by a grounded anisotropic slab are studied. These investigations reveal that a grounded slab consisting of an anisotropic zero/low index material can provide an extremely low value for the real part of the propagation constant of the leaky mode, thereby facilitating stable unidirectional broadside radiation over a wide frequency range. The truncation effect of the slab is then investigated through full-wave simulations, which is found to be beneficial for a practical implementation of dispersive metamaterials. Finally, to validate the proposed concept, a subwavelength end-loaded dipole array is designed to realize the required anisotropic zero-index property and is applied to a SIW fed longitudinal slot antenna for the 5.8 GHz wireless local area network (WLAN) band. Measurements of the fabricated antenna prototype are shown to be in strong agreement with simulation results, thus confirming the proposed antenna design. The resulting antenna is only $0.12 lambda $ thick, all while accomplishing a broadside gain of more than 10 dBi and a front-to-back ratio larger than 26 dB, which is $sim {hbox{7 dB}}$ and $sim {hbox{10 dB}}$ higher than that of the SIW fed slot alone, respectively. The $-{hbox{10 dB}}$ impedance bandwidth is more than 9% both with and without the presence of the MM coating. The proposed technique offers a means for realizing low-cost and low-profile unidirectional antennas with moderate bandwidth.
    IEEE Transactions on Antennas and Propagation 03/2014; 62(3):1173-1184. DOI:10.1109/TAP.2013.2294354 · 2.46 Impact Factor
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    ABSTRACT: In this paper, we demonstrate an ultra-thin, low-loss optical metamaterial filter with high transmission and near constant group delay across a broad pass-band from 3.0 to 3.5μ m. Deep-subwavelength air hole inclusions positioned at the corners of a conventional metallodiectric fishnet were used engineer the dispersive properties of the structure to have an impedance match to free space over the pass-band. The optical properties of the metamaterial filter were verified by experimentally fabricating and characterizing the optimized free-standing nano-notched fishnet. The measured experimental results agreed well with the simulated response, showing a high transmission band over the targeted wavelength band.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2014; DOI:10.1117/12.2045514 · 0.20 Impact Factor
  • Farhad A. Namin, Douglas H. Werner
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    ABSTRACT: A rigorous approach for the analysis of diffraction from quasicrystalline gratings is presented. Previous methods for determining the diffraction properties of quasicrystalline gratings have relied on periodic supercell approximations. Our method exploits the cut-and-project method, which constructs quasicrystals as irrational slices of higher-dimensional periodic structures onto the physical space. The periodicity in the higher-dimensional space allows for the application of Floquet’s theorem. The solutions can then be obtained by solving Maxwell’s equations in the higher-dimensional space and projecting the results to the lower dimensional physical space. As an example, the method is applied to a one-dimensional aperiodic grating based on a Fibonacci quasicrystal (QC) where the results that were generated are shown to be in near-perfect agreement with those obtained using the supercell approximations.
    02/2014; 1(3):212–220. DOI:10.1021/ph400066v
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    ABSTRACT: Nanostructured optical coatings with tailored spectral absorption properties are of interest for a wide range of applications such as spectroscopy, emissivity control, and solar energy harvesting. Optical metamaterial absorbers have been demonstrated with a variety of customized single band, multiple band, polarization, and angular configurations. However, metamaterials that provide near unity ab-sorptivity with super-octave bandwidth over a specified optical wavelength range have not yet been demonstrated experimentally. Here, we show a broadband, polarization-insensitive metamaterial with greater than 98% measured average absorptivity that is maintained over a wide ±45º field-of-view for mid-infrared wavelengths between 1.77 and 4.81 µm. The nearly ideal absorption is realized by using a genetic algorithm to identify the geometry of a single-layer metal nanostructure array that excites multiple overlapping electric resonances with high optical loss across greater than an octave band-width. The response is optimized by substituting palladium for gold to increase the infrared metallic loss and by introducing a dielectric superstrate to suppress reflection over the entire band. This demonstration advances the state-of-the-art in high-performance broadband metamaterial absorbers that can be reliably fabricated using a single patterned layer of metal nanostructures.
    ACS Nano 01/2014; 8(2). DOI:10.1021/nn4057148 · 12.03 Impact Factor
  • International Journal of Antennas and Propagation 01/2014; 2014:1-18. DOI:10.1155/2014/429837 · 0.83 Impact Factor
  • P.J. Gorman, M.D. Gregory, D.H. Werner
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    ABSTRACT: Recently, the covariance matrix adaption evolutionary strategy (CMA-ES) has received attention for outperforming conventional global optimization techniques such as the genetic algorithm (GA) or particle swarm optimization (PSO), often used in electromagnetic designs. Here, CMA-ES is first applied to the design of ultra-wideband aperiodic arrays using realistic spiral radiating elements. To improve the axial ratio of the array, optimization was extended to incorporate a mechanical rotation of each spiral element. This novel strategy of optimizing both the location and rotation of each element provides noticeable improvement in both the axial ratio and sidelobe level performance.
    IEEE Transactions on Antennas and Propagation 01/2014; 62(4):1663-1672. DOI:10.1109/TAP.2013.2287904 · 2.46 Impact Factor

Publication Stats

5k Citations
556.81 Total Impact Points

Institutions

  • 2014
    • Park University
      Parkville, Missouri, United States
  • 1991–2014
    • Pennsylvania State University
      • • Department of Electrical Engineering
      • • Applied Research Laboratory
      • • College of Engineering
      University Park, Maryland, United States
  • 2006–2013
    • William Penn University
      Worcester, Massachusetts, United States
    • York College of PA
      State College, Pennsylvania, United States
  • 2011
    • Northrop Grumman
      Falls Church, Virginia, United States
  • 2009–2010
    • University of Massachusetts Amherst
      • Department of Electrical and Computer Engineering
      Amherst Center, MA, United States
  • 2004–2010
    • University of Granada
      • Departamento de Electromagnetismo y Física de la Materia
      Granada, Andalusia, Spain
  • 2007
    • Urmia University
      Rezâiyye, Āz̄ārbāyjān-e Gharbī, Iran
  • 2003–2006
    • University of Massachusetts Lowell
      • Department of Electrical & Computer Engineering
      Lowell, MA, United States
    • Università di Pisa
      Pisa, Tuscany, Italy