Chandra Sekhar Kaipa

Publications (17) View all

• Article: Enhanced transmission with a graphene-dielectric microstructure at low-terahertz frequencies

  Chandra S. R. Kaipa, Alexander B. Yakovlev, George W. Hanson, Yashwanth R. Padooru, F. Medina, F. Mesa
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  ABSTRACT: Here, we report on the transmissivity of electromagnetic waves through a stack of monolayer graphene sheets separated by dielectric slabs at low-terahertz frequencies. It is observed that the multilayer structure possesses band-gap properties and supports a series of bandpass and band-stop regions, similar to the cases of stacked metallic meshes separated by dielectric slabs at microwave/THz frequencies and a metal-dielectric stack at optical frequencies. The transmission resonances in the bandpass region are identified as coupled Fabry-P´erot resonances associated with the individual cavities of dielectric slabs loaded with graphene sheets. It is also noticed that these resonances lie within a certain characteristic frequency band, independent of the number of layers in the graphene-dielectric stack. The study is carried out using a simple analytical transfer-matrix approach or, equivalently, a circuit-theory model, resulting in the exact solution for the multiple dielectric/graphene sheet surface-conductivity model. Also, an independent verification of the observed phenomena is obtained with commercial numerical simulations.
  Physical Review B 06/2012; 85:245407. · 3.69 Impact Factor
• Article: Indefinite dielectric response and all-angle negative refraction from a structure formed by deeply-subwavelength inclusions

  Chandra S. R. Kaipa, Alexander B. Yakovlev, Stanislav I. Maslovski, Mario G. Silveirinha
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  ABSTRACT: The realization of mesoscopic media that mimic an ideal continuous indefinite material remains a challenging problem, particularly because current designs are plagued by spatial dispersion effects and are based on inclusions whose size may be a significant fraction of the wavelength. Here we show that a structure formed by an array of inductively loaded metallic rods terminated by metallic patches at both ends may enable to largely overcome these problems, and imitate more closely indefinite dielectric media with a local response. In particular, we report a strong all-angle negative refraction effect, even in scenarios where the characteristic size of the material is deeply subwavelength. The response of the proposed structure is characterized using a homogenization model developed for the uniaxial wire medium with impedance loadings.
  Physical Review B 10/2011; 84:165135. · 3.69 Impact Factor
• Article: Circuit modeling of multiband high impedance surface absorbers in the microwave regime

  Yashwanth R. Padooru, Alexander B. Yakovlev, Chandra S. R. Kaipa, F. Medina, F. Mesa
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  ABSTRACT: In this paper, we present a simple circuit model to study the absorption of electromagnetic waves by a multilayer structure with a high impedance surface in the microwave regime. The absorber consists of a stack of two-dimensional arrays of sub-wavelength meshes or patches separated by dielectric slabs and backed by a metallic ground plane, with a single resistive sheet placed on the top layer. We observe the appearance of low-frequency resonances of total absorption, which have been identified as the resonances of Fabry-Pérot type associated with the individual reactively loaded dielectric slabs (that are strongly coupled through the subwavelength grids). It is shown that these resonances lie within certain characteristic frequency band defined by the structural parameters of the absorber. The observed resonances are characterized by studying the electromagnetic field behavior using the circuit model and full-wave numerical program. In addition, we show that the patch array absorber provides stable resonances with respect to the angle and the polarization of obliquely incident plane waves.
  Physical Review B 07/2011; 84:035108. · 3.69 Impact Factor
• Conference Proceeding: Multi-band High-Impedance Surface Absorbers with a single Resistive sheet: Circuit Theory Model

  Y. R. Padooru, A. B. Yakovlev, C. S. R. Kaipa, F. Medina, F. Mesa
  IEEE AP-S Symposium and USNC/URSI National Radio Science Meeting, Spokane, WA; 01/2011
• Conference Proceeding: Sub-Wavelength Transmission Through Stacked Two-dimensional Metallic Patches: A Circuit Model Perspective

  C. S. R. Kaipa, A. B. Yakovlev, F. Medina, F. Mesa, Y. R. Padooru
  IEEE AP-S Symposium and USNC/URSI National Radio Science Meeting, Spokane, WA; 01/2011