An experimental apparatus for measuring surface resistance in the submillimeter-wavelength region

Abstract

A simple comparative technique to characterize surface electrical resistance of small metallic samples at submillimeter wavelengths is presented. A quasioptical hemispherical resonator, fed by an optically pumped far-infrared laser is used, with the sample serving as the plane mirror. The cavity developed combines a small beam size at the sample, enabling measurements on samples with widths as small as 5 mm, with a large quality factor Q, so that surface resistance losses are readily measurable. This cavity uses a simple new geometry that feeds the cavity through a single small coupling hole that also serves as a system of monitoring energy storage in the cavity by means of a single external beamsplitter. An alternate approach of inserting an internal beamsplitter into the resonator was found to be unacceptable due to excessive losses and alignment problems.

Robust electromagnetic absorption by graphene/polymer heterostructures

“…This admittance-matching condition (see figure 1 and the explanations in the caption) yields d c 2 0 ϵ σ ≈ , assuming n 1 ≈ for both media. The validity of this formula breaks down for a very good conductor like Cu ( 4.5 10 7 σ = S/m at 35 GHz [3]), for it leads to a fraction of a nanometer. It is a useful indicator, however.…”

Understanding the Apparently Poor Conductivity of Galvanized Steel Plates

“…The same reason was suggested for galvanized and zincplated steels. In fact, recent results have proven that surface roughness cannot explain a more than 20-fold conductivity reduction: measurements up to 360 GHz were shown in [39] to result in less than 20% reduction compared to DC conductivity for silver samples; similar results are reported in [40] and [41] for the THz range, where the skin depth is also negligible compared to surface roughness; results in [42] for stainless steel up to 2 THz also show no major impact of surface roughness. A higher reduction of about 50% was reported in [43], but dealt with sub-micrometer thin films, thinner than the skin depth.…”

“…The models introduced in Section III predict that the apparent dissipative conductivity σa of GSP are expected to be highly variable because of: i) a transition region where σa approximatively scales linearly with the frequency, and ii) high variability of the coating equivalent conductivity σ c , depending on the coating technology. This last point was already empirically observed in [4], but apparent conductivities were only estimated at 8.42 GHz, since resonatorbased characterization techniques were used [4], [41], [51], as they are better suited to the characterization of good conductors [54], [55]. Wide-band techniques such as those based on transmission and reflection through waveguides [56], commonly used for dielectric materials, are not suitable for conductors, since their reflectivity is weakly sensitive to the metal conductivity, as clear from (3).…”

“…Given that σ b is complex, it is not immediately clear how it is related to power dissipation by a steel surface. Most experimental methods for measuring the conductivity of metals rely on power dissipation phenomena, e.g., in resonance cavities or waveguides [4], [41], [50], [51]. For this reason we suggest an alternative definition of the effective conductivity, based on the loss factor…”

Conductivity Extraction Using a 180 GHz Quasi-Optical Resonator for Conductive Thin Film Deposited on Conductive Substrate

“…Several kinds of surface resistance evaluation method have been described in literatures [ 49 , 50 , 51 , 52 , 53 ] to obtain . Among them, the quasi-optical resonator has been widely used and this method is compatible with the theoretical model presented above.…”