Affiliated with the
Communication & Space
Sciences Laboratory

Novel Electromagnetic Metamaterials

Micro-scale and Nano-scale Electromagnetics

All dielectric FSS design
  • Interest in controlling wavelengths of light reflected and transmitted by a thin planar surface.
  • Frequency Selective Surface (FSS) techniques developed for microwave applications can be scaled to micron dimensions to achieve infrared filtering from a single metallodielectric layer.
  • MDPCs designed using Fractal and Genetic Algorithm techniques produce multiple strong stopbands at far-IR wavelengths.
  • Success in the far-IR has prompted efforts to scale down to shorter wavelengths and pursue exciting technologies such as Negative Index Materials (NIM) and All-dielectric Frequency Selective Surfaces (DFSS).


FSS Unit Cells (Click on the image to enlarge it)

 

click on
Scanning electron microscope (SEM) images and measured transmission spectra (blue lines)
of microfabricated IR metallodielectric FSS filters with fractal cross-dipole, fractal square-patch, and GA-synthesized metallic geometries. Strong band rejection greater than 10 dB is
observed at designed IR wavelengths between 15 and 75 µm. PMM-simulated
transmission spectra with metallic and dielectric losses are included as red circles.
(Click on the image to enlarge it)

 

..: References :..

1-) Dual-band infrared single-layer metallodielectric photonic crystals
by Robert P. Drupp, Jeremy A. Bossard, Yong-Hong Ye, Douglas H. Werner, and Theresa S. Mayer
Applied Physics Letters, Vol. 85, No. 10, pp. 1835-1837, Sep 6, 2004.

ABSTRACT: Metallodielectric photonic crystals (MDPCs) consisting of periodic arrays of self-similar two-stage fractal patch metallic elements patterned on thin dielectric substrates are shown to exhibit excellent mid- and far-infrared dual-band response in a single layer structure. This was achieved by optimizing the element size and interelement spacing of cross-dipole and square-patch fractal elements using full-wave periodic method of moments modeling techniques that calculate electromagnetic scattering from the MDPC surface and are able to account for material loss and loading effects. All structures fabricated based on these designs had two measured stopbands with greater than 10 dB attenuation positioned at wavelengths determined by element geometry and size as well as interelement spacing. This simple single layer fractal MDPC geometry will facilitate further scaling into the near-IR wavelength regime.
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2-) Single-layer multiband infrared metallodielectric photonic crystals designed by genetic algorithm optimization
by Robert P. Drupp, Jeremy A. Bossard, Douglas H. Werner, and Theresa S. Mayer
Applied Physics Letters, Vol 86, 081102 (2005) , (3 pages) , 21 Feb 2005.

ABSTRACT: Metallodielectric photonic crystals (MDPCs) consisting of a planar periodic array of metallic patch elements designed by genetic algorithm (GA) optimization were patterned on flexible dielectric substrates and exhibit strong mid- and far-infrared (IR) dual-band response. The GA uses biological principles of natural selection to evolve nonintuitive geometries by optimizing the MDPC scattering response based on a user-defined fitness function. The transmission spectra measured on two different MDPCs optimized for optically thin and thick substrates have two strong stop bands with attenuation greater than 10 dB, which agree well with those predicted by full-wave periodic method of moments (PMM) modeling. This versatile GA optimization approach will facilitate design of scaled mid- and near-IR MDPCs with user-defined scattering response.
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3-) A Novel Design Methodology for Reconfigurable Frequency Selective Surfaces Using Genetic Algorithms
by Jeremy A. Bossard, Douglas H. Werner, Theresa S. Mayer, and Robert P. Drupp
IEEE Transactions on Antennas and Propagation, Vol 53, No. 4, pp. 1390-1400, April 2005.

ABSTRACT: In this paper, a new reconfigurable frequency selective surface (RFSS) design concept is introduced. A grid of simple metallic patches interconnected by a matrix of switches is proposed as the unit cell of an RFSS. The switches are independently addressable and provide significant transmission and reflection flexibility over a large range of frequencies. This flexibility is exploited by optimizing the switch settings using a genetic algorithm to produce a desired frequency response. The versatility of the design technique is demonstrated by presenting several examples of genetically optimized RFSS. The first example to be considered is a linearly polarized FSS that can be reconfigured for either single-, dual-, or tri-band operation. An RFSS design is also introduced that can be optimized to have a frequency response that is polarization independent in one state (i.e., for one combination of switch settings) and polarization dependent in another state.




4-) Multiband Planar Infrared Metallodielectric Photonic Crystals Designed Using Genetic Algorithms with Fabrication Constraints
by J. A. Bossard, J. A. Smith, D. H. Werner, T. S. Mayer, and R. P. Drupp

ABSTRACT: Planar metallodielectric photonic crystals (MDPCs) with multiple stop-bands in the far-infrared transmission spectrum have been designed using Frequency Selective Surface (FSS) techniques at the micron-scale. A genetic algorithm (GA) has been used to optimize MDPC designs that exhibit multiple stop-bands with greater than 10dB attenuation. It will be shown that by including design constraints in the GA to account for limitations in the fabrication process, it is still possible to synthesize a subset of MDPC structures that both meet the desired performance criteria and are capable of being accurately fabricated.




5-) Design of All-Dielectric Frequency Selective Surfaces Using Genetic Algorithms Combined with the Finite Element-Boundary Integral Method
by Ling Li and Douglas H. Werner

ABSTRACT: In this paper, a Genetic Algorithm (GA) design methodology is presented for the synthesis of doubly periodic all-dielectric Frequency Selective Surfaces (DFSS). The GA is used to optimize the dielectric constants of the material as well as the topology of the unit cell to produce the desired frequency response. The finite element-boundary integral method (FE-BI) is employed to efficiently evaluate the fitness of a candidate design.




6-) The Design and Fabrication of Planar Multiband Metallodielectric Frequency Selective Surfaces for Infrared Applications
by J. A. Bossard, D. H. Werner, T. S. Mayer, J. A. Smith, Y. U. Tang, R. P. Drupp, and Ling Li
IEEE Transactions on Antennas and Propagation, Vol. 54, No. 4, April 2006.

ABSTRACT: In this paper, micron-scale frequency selective surfaces (FSS) are presented for the first time that exhibit multiple strong stopbands (>10dB) in the far-infrared (IR). Fractal and genetic algorithm (GA) synthesis techniques are employed in the design of single-layer, multiband IR FSS. These designs have been fabricated on thin, flexible polyimide substrates and characterized using Fourier transform infrared (FTIR) spectroscopy. Measurements show excellent agreement with predictions from a periodic method of moments (PMoM) analysis technique that takes into account metallic and dielectric losses. Additional design constraints were incorporated into the GA in order to guarantee that the synthesized FSS structures could be accurately fabricated.




7-) A Novel Concept for Reconfigurable Frequency Selective Surfaes Based on Silicon Switches
by Xiaotao Liang, Douglas H. Werner, and Brian Weiner
Microwave and Optical Technology Letters, Vol. 49, No. 1, pp. 109 -114, January 2007.

ABSTRACT: The authors describe a novel concept for reconfigurable frequency selective surfaces based on metallic dipole and cross-dipole elements connected by switches on an exposed silicon substrate. As the conductivity of silicon can be varied over a large dynamic range by photonic excitation, it represents a good candidate substrate material for producing effective switches. The genetic algorithm was used to obtain optimal performance of the switch with respect to variations of the geometric and electrical parameters of the design for desired excitation frequencies.
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8-) Multiband All-Dielectric Frequency Selective Surface Filters for the Mid-Infrared
by Jeremy A. Bossard*, Seokho Yun, Yan Tang, Jacob A. Smith, Douglas H. Werner, and Theresa S. Mayer
2007 IEEE Antennas and Propagation International Symposium, pp. 3416 - 3419, 9-15 June 2007.





9-) Optical Antenna Effect in Semiconducting Nanowires
by G. Chen, Jian Wu, Qiujie Lu, H. R. Gutierrez, Qihua Xiong, M. E. Pellen, J. S. Petko, D. H. Werner, and P. C. Eklund
Nano Letters, Vol 8, Issue 12, April 19, 2008.

ABSTRACT : We report on investigations of the interaction of light with nanoscale antennae made from crystalline GaP nanowires (NWs). Using Raman scattering, we have observed strong optical antenna effects which we identify with internal standing wave photon modes of the wire. The antenna effects were probed in individual NWs whose diameters are in the range 40 < d < 300 nm. The data and our calculations show that the nature of the backscattered light is critically dependent on the interplay between a photon confinement effect and bulk Raman scattering. At small diameter, d < 65 nm, the NWs are found to act like a nearly perfect dipole antenna and the bulk Raman selection rules are masked leading to a polarized scattering intensity function IR ~ cos4θ. Underscoring the importance of this work is the realization that a fundamental understanding of the “optical antenna effect” in semiconducting NWs is essential to the analysis of all electro-optic effects in small diameter filaments.
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10-) Tunable Frequency Selective Surfaces and Negative-Zero-Positive Index Metamaterials Based on Liquid Crystals
by Jeremy A. Bossard, Xiaotao Liang, Ling Li, Seokho Yun, Douglas H. Werner, Brian Weiner, Theresa S. Mayer, Paul F. Christman, Andres Diaz, and I. C. Khoo
IEEE Transactions on Antennas and Propagation, Vol. 56, No. 5, pp. 1308 - 1320, May, 2008.

ABSTRACT: We utilize the properties of aligned nematic liquid crystal (LC) cells in the design of: (i) a new type of metamaterial whose index of refraction is tunable from negative, through zero, to positive values and (ii) micron-scale metallodielectric and all-dielectric tunable frequency selective surfaces (FSSs). The metamaterial is constructed by randomly doping a liquid crystal substrate with coated dielectric (non-magnetic) spheres and can be utilized over a large spectral range. FSSs with a liquid crystal superstrate are synthesized using conventional and genetic algorithm methods to exhibit broadband tunable filter characteristics at mid-infrared (mid-IR) wavelengths. These LC tunable FSS structures can be used to develop a new class of infrared/optical switches for terahertz applications.





11-) Single-layer metallodielectric nanostructures as dual-band midinfrared filters
by Yan Tang, Jeremy A. Bossard, Douglas H. Werner, and Theresa S. Mayer
Applied Physics Letters, 92, 263106 (2008)

ABSTRACT: We report a design and fabrication strategy for creating single-layer metallodielectric nanostructures with dual-band filtering properties at midinfrared wavelengths. Genetic algorithm optimization was used to determine an arrangement of nanometer-scale metal pixels within one unit cell of a two-dimensional periodic array that best satisfied the user-specified filter response and nanofabrication design rule constraints. Infrared transmission and reflection spectra measured on an optimized nanostructure array had two narrow stop bands blueshifted by 0.2 µm from the designed center wavelengths of 3.3 and 4.1 µm, with transmission attenuation greater than -20 dB and reflection attenuation less than -1.5 dB in each band. This strategy provides a practical and efficient approach to design metallodielectric nanostructures needed for photonic device applications as well as for future low-loss refractive index engineered metamaterials.
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12-) Angle and polarization tolerant midinfrared dielectric filter designed by genetic algorithm optimization
by Seokho Yun, Jeremy A. Bossard, Theresa S. Mayer, and Douglas H. Werner
Applied Physics Letters, 96, 223101 (2010)

ABSTRACT: We report a dielectric frequency selective surface filter with an angularly tolerant, polarization independent stop band designed at a midinfrared wavelength of 3.0 μm. The structure, consisting of a doubly-periodic amorphous silicon grating supported by a polyimide membrane, was optimized using a genetic algorithm to have a transmission stop band with a 3.33% 10 dB bandwidth for incidence angles as large as 10 ° from normal. The measured properties of the fabricated filter were within 1% of theoretical predictions. This strategy provides a practical and efficient approach to creating advanced dielectric filters for highly customized infrared optical device and coating applications.
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13-) Characterization of complementary patterned metallic membranes produced simultaneously by a dual fabrication process
by Qingzhen Hao, Yong Zeng, Xiande Wang, Yanhui Zhao, Bei Wang, I-Kao Chiang, Douglas H. Werner, Vincent Crespi, and Tony Jun Huang
Applied Physics Letters, 97, 193101 (2010)

ABSTRACT: An efficient technique is developed to fabricate optically thin metallic films with subwavelength patterns and their complements simultaneously. By comparing the spectra of the complementary films, we show that Babinet's principle nearly holds for these structures in the optical domain. Rigorous full-wave simulations are employed to verify the experimental observations. It is further demonstrated that a discrete-dipole approximation can qualitatively describe the spectral dependence of the metallic membranes on the geometry of the constituent particles as well as the illuminating polarization.
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14-) Metamaterials with custom emissivity polarization in the near-infrared
by Jeremy A. Bossard and Douglas H. Werner
Optics Express, Vol. 21, No. 3, 3872-3884 (2013)

ABSTRACT: Metamaterials have been previously studied for their ability to tailor the dispersive infrared (IR) emissivity of a surface. Here, we investigate metamaterial coatings based on an electromagnetic band-gap surface for use as near-IR emitters with custom polarization selectivity. A genetic algorithm is successfully employed to optimize the metamaterial structures to exhibit custom linear, circular, and elliptical polarization. A study is also conducted on a bi-anisotropic slab, showing that anisotropic chirality is required in the metamaterial structure in order to achieve circular or elliptical emissivity polarization.
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15-) Metamaterials with angle selective emissivity in the near-infrared
by Jeremy A. Bossard and Douglas H. Werner
Optics Express, Vol. 21, No. 5, 5215-5225, Mar. 2013

ABSTRACT: Metamaterials have been previously studied for their ability to tailor the dispersive IR emissivity of a surface. Here, we investigate two metamaterial structures based on an electromagnetic band-gap surface and a dielectric resonator array for use as near-IR emitters with custom angle selectivity. A genetic algorithm is successfully employed to optimize the metamaterial structures to have minimum emissivity in the normal direction and high emissivity at custom off-normal angles specified by the designer. Two symmetry conditions are utilized to achieve emissivity patterns that are azimuthally stable or distinct in the two orthogonal plane cuts.
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16-) Near-ideal optical metamaterial absorbers with super-octave bandwidth
by Jeremy A. Bossard, Lan Lin, Seokho Yun, Liu Liu, Douglas H. Werner, and Theresa S. Mayer
ACS Nano, Vol. 8, No. 2, 1517-1524, Jan. 2014

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 absorptivity 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 ±45° 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 bandwidth. 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.
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