THz characterization of high dielectric‐constant materials using double‐layer sample

Abstract

The super-hyper singular integrals in the EFIE of the second form in Eq. (1) were prohibitive and there was no direct way to evaluate them. But we have developed a novel technique to efficiently handle such singularities based on the series representation of the Green's function and a constant current approximation. The approach allows us to solve the EFIE of the second form directly. It has locality in its unknown association with space, and hence is easy to incorporate with FMA. The derived closed-form formulas can be used to calculate both selfinteraction and near-interaction terms in the impedance matrix very accurately and conveniently. The numerical errors in the scheme mainly come from the lower-order approximation for current and geometry. We can easily implement the higherorder approximation of current in the scheme because the introduction of higher-order terms only weakens the degree of singularity. We will incorporate the higher-order representation of geometry for the scheme in the future and improve the overall accuracy further. ABSTRACT: A method of measurement of the real and imaginary parts of high dielectric constant materials at THz frequencies is described. The method is based on application of double-layer sample with variable distance between slabs. The recorded power transmittance inerferogram is employed for reconstructing complex permittivity of a material under test. Reconstructing algorithm and its realization are presented. Example of measurements of the alumina sample in 0.8 -1.1 THz has demonstrated a good agreement with independent data obtained from the time-domain terahertz spectroscopy method. ABSTRACT: Negative-permeability sub-wavelength particles, namely split-ring resonators and spiral resonators, are compared and their performances analyzed for a different number of concentric rings and spiral turns, respectively. Left-handed lines are designed, fabricated, and measured that use multiple complementary split-ring and spiral resonators. More compact structures are obtained, with improved characteristics.

Complex Permittivity Determination of Lossy Materials at Millimeter and Terahertz Frequencies Using Free-Space Amplitude Measurements

“…It has long been known from microwave measurements that transmission measurements are more stable and provide information on the whole volume of the sample under test [15,[29][30][31]. In this paper, our aim is to propose a measurement method and a fast retrieval algorithm for relative complex permittivity (ε r ) measurements of lossy materials using transmission properties of a BWO set-up operating at mm-and THz frequencies, because of the attractive features of BWO oscillators just discussed.…”

“…A plethora of potential application scenarios are foreseen for mm-waves and THz spectroscopy systems. Applications include non-destructive testing of industrial processes and products [3] and of cultural heritage [4], detection of hazardous materials and concealed weapons [5], and so on [6][7][8][9][10][11][12][13], and measurement of lowloss dielectric materials which are now of increasing importance in the design of circuit components and quasi-optical elements such as multilayer filters, dielectric (or semiconductor) windows, beam splitters and absorbers, switches, and directional couplers [14][15][16].…”

“…The accurate information about electrical properties of materials is needed for design and fabrication of a variety of components operating in mm-waves and THz [14,15]. It has long been known from microwave measurements that transmission measurements are more stable and provide information on the whole volume of the sample under test [15,[29][30][31].…”

“…In this paper, our aim is to propose a measurement method and a fast retrieval algorithm for relative complex permittivity (ε r ) measurements of lossy materials using transmission properties of a BWO set-up operating at mm-and THz frequencies, because of the attractive features of BWO oscillators just discussed. Inasmuch as only the intensity of transmission properties can be measured by a BWO set-up, an extra datum to extract enough information for ε r is obtained from the Fabry-Perot effect [15] by varying the distance between identical dielectric slabs. Periodicity, swing and height of interference maxima (and minima) depend on both real and imaginary parts of ε r .…”

“…In the second measurement configuration of mm-waves and THz systems, narrowband measurements are carried out using various sources such as two single mode lasers (photomixing) [1,25] and a backward-wave oscillator (BWO) [1,15,26,27]. Photomixing of two continuous wave laser beams holds more premise than TDS because (a) the THz frequency and line-width are pre-selected by the choice of the laser wavelengths and line widths, and (b) compact and inexpensive semiconductor lasers are gradually becoming accessible for such applications [25].…”