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Akhlesh Lakhtakia - One of the best experts on this subject based on the ideXlab platform.

  • enhanced left right asymmetry in reflection and transmission due to a periodic multilayer of a topological insulator and an anisotropic Dielectric Material
    Applied Optics, 2019
    Co-Authors: Francesco Chiadini, Akhlesh Lakhtakia, Vincenzo Fiumara, Antonio Scaglione
    Abstract:

    Very weak left/right asymmetry in reflection and transmission is offered by a layer of a topological insulator on top of a layer of an anisotropic Dielectric Material, but it can be enhanced very significantly by using a periodic multilayer of both types of Materials. This is an attractive prospect for realizing one-way terahertz devices, because both types of Materials can be grown using standard physical-vapor-deposition techniques.

  • on optical absorption peaks in a nonhomogeneous Dielectric Material over a two dimensional metallic surface relief grating
    Nanostructured Thin Films X 2017, 2017
    Co-Authors: Faiz Ahmad, Thomas Anderson, Benjamin J Civiletti, Peter Monk, Akhlesh Lakhtakia
    Abstract:

    The rigorous coupled-wave approach (RCWA) was used to calculate the optical absorption in a Dielectric Material deposited over a two-dimensional (2D) metallic surface-relief grating. The Dielectric Material was taken to be nonhomogeneous in the direction normal to the mean plane of the grating. The grating was chosen to comprise hillocks on a square grid. On illumination by a monochromatic plane waves, the chosen structure should support the excitation of two types of guided-wave modes: surface-plasmon-polariton (SPP) waves and waveguide modes (WGMs). Two cases were considered: (i) a 1D photonic crystal made from layers of silicon oxynitrides of differing composition, and (ii) a tandem solar cell comprising three amorphous-silicon p-i-n junctions. Optical absorption was studied in relation to the direction of propagation, polarization state, and the free-space wavelength of the incident plane wave. Several but not all absorptance peaks were correlated with the excitations of SPP-wave modes and WGMs predicted by the solutions of the underlying canonical boundary-value problems for guided-wave propagation. Some peaks of useful absorptances in the solar cell were also predicted by solutions of the canonical problems.

  • compound surface plasmon polariton waves guided by a thin metal layer sandwiched between a homogeneous isotropic Dielectric Material and a periodically multilayered isotropic Dielectric Material
    arXiv: Optics, 2015
    Co-Authors: Francesco Chiadini, V Fiumara, Antonio Scaglione, Akhlesh Lakhtakia
    Abstract:

    Multiple p- and s-polarized compound surface plasmon-polariton (SPP) waves at a fixed frequency can be guided by a structure consisting of a metal layer sandwiched between a homogeneous isotropic Dielectric (HID) Material and a periodic multilayered isotropic Dielectric (PMLID) Material. For any thickness of the metal layer, at least one compound SPP wave must exist. It possesses the p-polarization state, is strongly bound to the metal/HID interface when the metal thickness is large but to both metal/Dielectric interfaces when the metal thickness is small. When the metal layer vanishes, this compound SPP wave transmutes into a Tamm wave. Additional compound SPP waves exist, depending on the thickness of the metal layer, the relative permittivity of the HID Material, and the period and the composition of the PMLID Material. Some of these are p polarized, the others being s polarized. All of them differ in phase speed, attenuation rate, and field profile, even though all are excitable at the same frequency. The multiplicity and the dependence of the number of compound SPP waves on the relative permittivity of the HID Material when the metal layer is thin could be useful for optical sensing applications.

  • composite surface plasmon polariton waves guided by a thin metal layer sandwiched between a homogeneous isotropic Dielectric Material and a periodically multilayered isotropic Dielectric Material
    Journal of Nanophotonics, 2015
    Co-Authors: Francesco Chiadini, V Fiumara, Antonio Scaglione, Akhlesh Lakhtakia
    Abstract:

    Multiple p - and s - polarized compound surface-plasmon-polariton (SPP) waves at a fixed frequency can be guided by a structure consisting of a metal layer sandwiched between a homogeneous isotropic Dielectric (HID) Material and a periodic multilayered isotropic Dielectric (PMLID) Material. For any thickness of the metal layer, at least one compound SPP wave must exist. It possesses the p - polarization state, and is strongly bound to the metal/HID interface when the metal thickness is large but to both metal/Dielectric interfaces when the metal thickness is small. When the metal layer vanishes, this compound SPP wave transmutes into a Tamm wave. Additional compound SPP waves exist, depending on the thickness of the metal layer, the relative permittivity of the HID Material, and the period and composition of the PMLID Material. Some of these are p - polarized, the others are s - polarized. All of them differ in phase speed, attenuation rate, and field profile, even though all are excitable at the same frequency. The multiplicity and dependence of the number of compound SPP waves on the relative permittivity of the HID Material when the metal layer is thin could be useful for optical sensing applications and intrachip plasmonic optical communication.

  • dyakonov tamm waves guided jointly by an ordinary isotropic homogeneous Dielectric Material and a hyperbolic Dielectric structurally chiral Material
    arXiv: Optics, 2014
    Co-Authors: Akhlesh Lakhtakia, Muhammad Faryad
    Abstract:

    The planar interface of an ordinary, isotropic, homogeneous, Dielectric Material and a hyperbolic, Dielectric, structurally chiral Material can support the propagation of one or multiple Dyakonov-Tamm waves, at a specified frequency and along a specified direction in the interface plane. When multiple Dyakonov-Tamm waves can exist, they differ in phase speed, propagation length, degree of localization to the interface, and spatial profiles of the associated electromagnetic fields. Dependence on the relative permittivity scalar of the isotropic partnering Material suggests exploitation for optical sensing of analytes.

Achmad Munir - One of the best experts on this subject based on the ideXlab platform.

  • Cylindrical coordinate system-based FDTD method for analysis of THz circular waveguide coated by Dielectric Material
    2016 22nd Asia-Pacific Conference on Communications (APCC), 2016
    Co-Authors: Antrisha Daneraici Setiawan, Achmad Munir
    Abstract:

    This paper presents the analysis of reflectivity and transmissivity for terahertz (THz) circular waveguide coated by Dielectric Material using cylindrical coordinate system-based finite difference time domain (FDTD) method. The analysis is conducted by discretizing a model of THz circular waveguide with the radius of 50μm and the length of 250μm. The scattering parameters in term of reflectivity and transmissivity are extracted from the electric fields obtained at different observation planes. Some scenarios in the analysis of reflectivity and transmissivity are applied by varying the thickness of coated Dielectric Material inside the circular waveguide compared to the hollow circular waveguide. Others scenarios are carried out by introducing some values of conductivity into the Dielectric Material. From the results, it is shown that resonant frequencies of circular waveguide coated by Dielectric Material in transverse electric (TE) mode are lower than the hollow waveguide. It also shows that the circular waveguide coated by Dielectric Material with the thickness of 7.5μm and the conductivity of 250S/m has better transmissivity than the hollow circular waveguide.

  • artificial Dielectric Material for lowering resonant frequency of microstrip circular patch antenna
    International Symposium on Intelligent Signal Processing and Communication Systems, 2015
    Co-Authors: Aditya Gianto Hadiwijaya, Achmad Munir
    Abstract:

    In this paper, the implementation of artificial Dielectric Material is proposed to lower resonant frequency of conventional microstrip circular patch antenna. The artificial Dielectric Material is applied to replace the Dielectric Material of conventional microstrip circular patch antenna which is designed based on TM11 resonance mode. The development of artificial Dielectric Material is implemented by incorporating cylindrical conductors into FR4 Epoxy Dielectric substrate used as host Material. Here, the conventional microstrip circular patch antenna is designed to resonate at frequency of 2.4GHz. From characterization result, it shows that the resonant frequency of proposed antenna with artificial Dielectric Material can be lowered up to 1.648GHz. Hence there is an increase of effective permittivity of artificial Dielectric Material around 212.2%.

  • extraction of anisotropic thin slab artificial Dielectric Material property using rectangular waveguide
    International Conference on Electrical Engineering and Informatics, 2015
    Co-Authors: Zaki Abdurrasyid, Muhammad Reza Hidayat, Achmad Munir
    Abstract:

    In this paper, the formulas for extracting the property of anisotropic thin slab artificial Dielectric Material using rectangular waveguide is proposed. The property of Material to be extracted in the current work is its relative permittivity. The anisotropic thin slab artificial Dielectric Material constructed of strip conductors on Dielectric substrates is piled up in some configurations. To verify the proposed formulas, simulations for some Dielectric Materials already known their relative permittivities such as FR4 Epoxy and Corning Materials are performed for verifying the extraction process. Then, the formulas are employed to extract unknown property of anisotropic thin slab artificial Dielectric Material. From the results, it is shown that the proposed formulas are successfully implemented for extracting the property of known Dielectric Materials with the maximum error of 5.208%. Furthermore, it is found that the anisotropic thin slab artificial Dielectric Material with vertical strip conductors has relative permittivity in the vertical direction bigger than in the horizontal direction. This also applies for the Material with horizontal strip conductors which has relative permittivity in the horizontal direction bigger than in the vertical direction.

  • Scattering parameters extraction of Dielectric loaded circular waveguide using cylindrical coordinate system-based FDTD method
    2015 International Seminar on Intelligent Technology and Its Applications (ISITIA), 2015
    Co-Authors: Ershad Junus Amin, Achmad Munir
    Abstract:

    The scattering parameters of circular waveguide loaded with Dielectric Material is proposed to be extracted using a method of finite-difference time-domain (FDTD) based on cylindrical coordinate system. The extraction of scattering parameters, i.e. reflection coefficient (S11) and transmission coefficient (S21), are performed by the electric fields obtained on different observation planes closed to the Dielectric Material. Some isotropic Dielectric Material which partially and fully loaded circular waveguide are included in the analysis. To validate the result of FDTD method, another analysis is carried out by using finite element method (FEM) commercialized software. Furthermore, the FDTD method is also applied to analysis a circular waveguide loaded with some anisotropic Dielectric Material. From the result, it shows that the proposed FDTD method has a good agreement qualitatively compared to the commercialized software with some discrepancy on the extraction result less than 3% for isotropic Dielectric Material loaded circular waveguide. Meanwhile, there is no result comparison for anisotropic Dielectric Material loaded circular waveguide due to an inability of commercialized software to perform a simulation in cylindrical coordinate system.

  • Resonant frequency computation of Dielectric Material loaded circular waveguide using cylindrical coordinate system-based FDTD method
    2015 International Conference on Electrical Engineering and Informatics (ICEEI), 2015
    Co-Authors: Antrisha Daneraici Setiawan, Hardi Nusantara, Achmad Munir
    Abstract:

    In this paper, a cylindrical coordinate system-based finite difference time domain (FDTD) method is proposed for resonant frequency computation of Dielectric Material loaded circular waveguide. The computation is carried out by discretizing a model of circular waveguide resonator which has the radius of 10.12mm and the length of 60mm using FDTD notation and numerically computed to determine its resonant frequency in transverse electric (TE) mode. Some scenarios are applied for loading the waveguide by Dielectric Materials to analyze its resonant frequency to be compared with the hollow circular waveguide. From the results, it is shown that the TE mode resonant frequency for loaded circular waveguide is lower than of hollow circular waveguide which satisfies the numerical prediction. Meanwhile, from the scenario of circular waveguide partially loaded with Dielectric Material which is coated from outer region in a certain depth, it is found that the resonant frequency varies depending on the depth of Dielectric Material or on the volume proportion of Dielectric Material in the waveguide. The result shows when the proportion of Dielectric Material is 36% the lower resonant frequency is similar with the waveguide fully loaded with Dielectric Material.

John A Polo - One of the best experts on this subject based on the ideXlab platform.

  • dyakonov tamm waves guided by the planar interface of an isotropic Dielectric Material and an electro optic ambichiral reusch pile
    Journal of The Optical Society of America B-optical Physics, 2011
    Co-Authors: John A Polo, Akhlesh Lakhtakia
    Abstract:

    The existence of an electromagnetic surface wave—classified as a Dyakonov–Tamm wave—guided by the planar interface of an isotropic, homogenous, Dielectric Material and an electro-optic ambichiral Reusch pile was theoretically established for various values of a dc electric field applied normal to the interface. For low magnitudes of the dc electric field, the spread of values of the refractive index ns of the isotropic partnering Material supporting the surface waves is exceedingly small. A sufficient increase in the magnitude of the dc electric field considerably widens that range. The allowed propagation directions, in all cases, constitute an angular sector of several tens of degrees in width.

  • theory of dyakonov tamm waves at the planar interface of a sculptured nematic thin film and an isotropic Dielectric Material
    Journal of Optics, 2009
    Co-Authors: John A Polo, Akhlesh Lakhtakia, Kartiek Agarwal
    Abstract:

    In order to ascertain the conditions for surface-wave propagation guided by the planar interface of an isotropic Dielectric Material and a sculptured nematic thin film (SNTF) with periodic nonhomogeneity, we formulated a boundary-value problem, obtained a dispersion equation therefrom, and numerically solved it. The surface waves obtained are Dyakonov–Tamm waves. The angular domain formed by the directions of propagation of the Dyakonov–Tamm waves can be very wide (even as wide as to allow propagation in every direction in the interface plane), because of the periodic nonhomogeneity of the SNTF. A search for Dyakonov–Tamm waves is, at the present time, the most promising route to take for experimental verification of surface-wave propagation guided by the interface of two Dielectric Materials, at least one of which is anisotropic. That would also assist in realizing the potential of such surface waves for optical sensing of various types of analytes infiltrating one or both of the two Dielectric Materials.

  • theory of dyakonov tamm waves at the planar interface of a sculptured nematic thin film and an isotropic Dielectric Material
    arXiv: Optics, 2009
    Co-Authors: John A Polo, Akhlesh Lakhtakia, Kartiek Agarwal
    Abstract:

    In order to ascertain conditions for surface-wave propagation guided by the planar interface of an isotropic Dielectric Material and a sculptured nematic thin film (SNTF) with periodic nonhomogeneity, we formulated a boundary-value problem, obtained a dispersion equation therefrom, and numerically solved it. The surface waves obtained are Dyakonov-Tamm waves. The angular domain formed by the directions of propagation of the Dyakonov--Tamm waves can be very wide (even as wide as to allow propagation in every direction in the interface plane), because of the periodic nonhomogeneity of the SNTF. A search for Dyakonov-Tamm waves is, at the present time, the most promising route to take for experimental verification of surface-wave propagation guided by the interface of two Dielectric Materials, at least one of which is anisotropic. That would also assist in realizing the potential of such surface waves for optical sensing of various types of analytes infiltrating one or both of the two Dielectric Materials.

  • electrical control of surface wave propagation at the planar interface of a linear electro optic Material and an isotropic Dielectric Material
    Electromagnetics, 2008
    Co-Authors: Sudarshan R Nelatury, John A Polo, Akhlesh Lakhtakia
    Abstract:

    Abstract Surface waves can propagate on the planar interface of a linear electro-optic (EO) Material and an isotropic Dielectric Material for restricted ranges of the orientation angles of the EO Material and the refractive index of the isotropic Material. These ranges can be controlled by the application of a DC electric field, and depend on both the magnitude and the direction of the DC field. Thus, surface-wave propagation can be electrically controlled by exploiting the Pockels effect.

  • dyakonov tamm wave at the planar interface of a chiral sculptured thin film and an isotropic Dielectric Material
    Journal of the European Optical Society: Rapid Publications, 2007
    Co-Authors: Akhlesh Lakhtakia, John A Polo
    Abstract:

    Surface waves, named here as Dyakonov--Tamm waves, can exist at the planar interface of an isotropic Dielectric Material and a chiral sculptured thin film (STF). Due to the periodic nonhomogeneity of a chiral STF, the range of the refractive index of the isotropic Material is smaller but the range of the propagation direction in the interface plane is much larger, in comparison to those for the existence of Dyakonov waves at the planar interface of an isotropic Dielectric Material and a columnar thin film.

Guohua Chen - One of the best experts on this subject based on the ideXlab platform.

  • freeze drying with Dielectric Material assisted microwave heating
    Aiche Journal, 2007
    Co-Authors: Guohua Chen
    Abstract:

    Experimental and theoretical investigations were conducted with regard to the effects of a Dielectric Material on freeze drying with microwave heating. The experimental results show that the Dielectric Material can effectively enhance the microwave freeze drying process, and substantial drying time can be saved compared with conventional freeze drying under the operating conditions tested. Theoretical study was performed by numerically solving a heat and mass transfer model of freeze drying with hygroscopic effect using the finite difference method with a moving boundary. The simulation results demonstrate the effectiveness of using the Dielectric Material in microwave freeze drying, especially when the solid content of the solution to be freeze dried is very low or the solid product has a very small loss factor. Comparisons of the drying curves display good agreements between experimental measurements and model predictions. Based on the profiles of the ice saturation and temperature, mechanisms of heat and mass transfer inside the Material were analyzed, and the drying rate-controlling factor was discussed. © 2007 American Institute of Chemical Engineers AIChE J, 2007

  • heat and mass transfer model of Dielectric Material assisted microwave freeze drying of skim milk with hygroscopic effect
    Chemical Engineering Science, 2005
    Co-Authors: Wei Wang, Guohua Chen
    Abstract:

    Abstract A new porous media mathematical model for freeze-drying was developed based on the adsorption–desorption relationship proposed in this paper. A finite difference solution was obtained from a moving boundary problem for the Dielectric-Material-assisted microwave freeze-drying process. Silicon carbide (SiC) was selected as the Dielectric Material; and frozen skim milk was used as the aqueous solution to be dried. Simulation results showed that the Dielectric Material can significantly enhance the microwave freeze-drying process. The drying time was 33.1% shorter than that of ordinary microwave freeze-drying under typical operating conditions. When the solid content of the solution to be freeze-dried was very low, or the solid product had a very small loss factor, microwave heating was less effective without the assistance of Dielectric Material. The mechanisms of heat and mass transfer during drying were analyzed based on profiles of ice saturation, temperature and vapor concentration. Drying rate-controlling factors were discussed. A comparison was made between the model predictions and the reported experimental data.

Qingwei Liao - One of the best experts on this subject based on the ideXlab platform.

  • a low sintering temperature low loss microwave Dielectric Material znzrnb2o8
    Journal of the American Ceramic Society, 2012
    Co-Authors: Qingwei Liao, Lingxia Li, Xiaoxu Yu, Mingjing Wang
    Abstract:

    A low sintering temperature microwave Dielectric Material ZnZrNb2O8 was reported. It exhibits a monoclinic structure, belongs to the space group P2/c (C2h4), and Z = 1. The Dielectric constant increased with increasing relative density. The Qf value increased with increasing packing fraction. The τf increased with increasing Dielectric constant. The typical values of ZnZrNb2O8 were e = 30, Qf = 61 000 GHz, τf=−52 × 10−6 °C−1, sintered at 950°C.

  • an ultra broad working temperature Dielectric Material of batio3 based ceramics with nd2o3 addition
    Journal of the American Ceramic Society, 2012
    Co-Authors: Dong Guo, Qingwei Liao, Wangsuo Xia, Yemei Han, Yin Peng
    Abstract:

    An ultra-broad working temperature Dielectric Material, BaTiO3–Na0.5Bi0.5TiO3–Nb2O5–MgO–Glass with Nd2O3 addition, was investigated for the first time. Microstructure and Dielectric properties of the well-sintered samples were studied. XRD results showed the formation of tetragonal perovskite and the presence of a second phase of NaBiTi6O14. It is found that the addition of Nd2O3 produces a decrease in tetragonality of perovskite structure which could be interpreted by the substitution of Nd3+ ions into Ti sites. Bulk densities and Dielectric properties were measured as a function of Nd2O3 concentration. The 0.4 mol% Nd2O3-doped sample showed the optimal Dielectric performance (er = 1445, tan δ<2.0%, ΔC/C ≤±12%) that satisfied EIA-X9R specification. In particular, the ceiling working temperature was significantly enhanced from 200°C to 270°C by doping Nd2O3. Since it possesses large Dielectric constant, low Dielectric loss, and stable temperature character, this Material shows promising applications for the ultra-broad temperature range components, e.g., multilayer ceramic capacitors.

  • new low loss microwave Dielectric Material zntinbtao8
    Journal of the American Ceramic Society, 2011
    Co-Authors: Qingwei Liao, Lingxia Li, Xiang Ding
    Abstract:

    A new low-loss, low-temperature sinterable microwave Dielectric Material ZnTiNbTaO8 was investigated for the first time. Single phase ZnTiNbTaO8 was obtained by the conventional solid-state route and sintered at 1120°C–1200°C for 6 h. Theoretical density, packing fraction, bond valence, and oxygen octahedron distortion were calculated. The excellent microwave Dielectric properties of e = 36.3, Qf = 67 000 GHz, τf =−57.66 × 10−6/°C were obtained from the new ZnTiNbTaO8 Materials sintered at 1140°C for 6 h.