Propagation modes on a dielectric coated wire

Zelby, Leon W.

doi:10.1016/0016-0032(62)90398-8

Cited by 13 publications

(6 citation statements)

References 7 publications

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“…We find that along the metal wire, the terahertz pulses propagate as surface waves, for which we can calculate the dispersion relation using a similar method as reported previously. 11,12 Due to the cylindrical symmetry, the solutions of Maxwell's equations for the magnetic and the electric fields are Bessel functions. We consider only the TM 00 mode as it can be shown that for thin coatings this is the only mode with little absorption, which will survive after 4 cm of propagation.…”

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Effect of a dielectric coating on terahertz surface plasmon polaritons on metal wires

Valk

Planken

2005

Applied Physics Letters

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The authors present measurements and calculations on the effect of thin dielectric coatings on the propagation of terahertz pulses along the surface of metal wires. Our measurements show that propagation over only a few centimeters of wire having a thin dielectric coating, strongly distorts the terahertz pulse, which results in a several tens of picoseconds long chirped signal. We demonstrate that the terahertz pulses propagate along the wire as surface waves, and show how a thin coating of a nondispersive material makes this propagation strongly dispersive, giving rise to the chirped signal observed in the measurements. Our results show the potential of terahertz surface plasmon polaritons on metal wires for the sensitive detection of thin dielectric layers. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.2011773͔ Recently, there has been an increased interest in the search for a good waveguide for the transportation of terahertz radiation. [1][2][3][4][5][6] The latest development in this field is the propagation of terahertz waves along bare metal wires with very little absorption and dispersion. 7,8 Indeed, measurements were shown in which two metal wires were combined to form what could eventually become a medical probe. Many metal wires, however, are not bare. Thin dielectric layers can often be found on the surface of metal wires, applied intentionally or unintentionally through oxidation or contamination, and the effects of these layers on the propagation of terahertz pulses along the wire are not wellknown.Here we show measurements and calculations on the propagation of terahertz pulses over copper wires with and without a thin polyurethane coating. Our time-domain measurements of a terahertz pulse propagating along a 4 cm long wire show that a coating of tens of micrometers thickness strongly distorts the terahertz pulse resulting in a chirped terahertz signal that lasts tens of picoseconds. A comparison with calculations based on Maxwell's equations shows that the terahertz pulses propagate along the wire as surface plasmon polaritons, and that the distortion of the terahertz pulse originates from the dispersive propagation of these waves along the coated wire. Remarkably, the propagation is dispersive, although we assume that the coating material itself has a frequency-independent refractive index. Our work indicates that thin coatings can seriously distort terahertz pulses propagating along metal wires. At the same time, however, this offers the possibility of using metal wires as sensitive detectors of thin layers. Figure 1 shows a schematic drawing of our setup. The terahertz pulses from our emitter are focused onto one of two types of metal wires. The first wire is a bare copper wire with a diameter of 1 mm. The second wire is a copper wire with a diameter of 1 mm having a polyurethane coating, specified to be about 34 m thick.9 A sharp copper needle is used to couple the terahertz radiation onto the wire. 8 The terahertz surface plasmon polariton propagates over the wire toward the detecti...

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“…We consider only the TM 00 mode as it can be shown that for thin coatings this is the only mode with little absorption, which will survive after 4 cm of propagation. 11 For this mode, the nonzero components of the electric and magnetic fields are written as…”

mentioning

confidence: 99%

Effect of a dielectric coating on terahertz surface plasmon polaritons on metal wires

Valk

Planken

2005

Applied Physics Letters

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“…Since the separation of contiguous resonators is much smaller than the wavelength, the excitation of the odd coplanar-stripline mode can be neglected [30]. Higher-order modes in the PGL decay rapidly, similarly to the Goubau line's [31], [32], and therefore were also neglected. Naturally, the line feeding the filter was modeled as a PGL with 𝛾 𝑝 and 𝑍 𝑝 .…”

Section: A Transmission-line Modelmentioning

confidence: 99%

Capacitively-Coupled Resonators for Terahertz Planar-Goubau-Line Filters

Cabello-Sanchez

Drakinskiy

Stake

et al. 2023

IEEE Trans. THz Sci. Technol.

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Low-loss planar Goubau lines show promising potential for terahertz applications. However, a single-wire waveguide exhibits less design freedom than standard multi-conductor lines, which is a significant constraint for realizing standard components. Existing filters for planar Goubau line lack clear design procedures preventing the synthesis of an arbitrary filter response. In this work, we present a design for a bandpass/bandstop filter for planar Goubau line by periodically loading the line with capacitively-coupled 𝜆∕2 resonators, which can be easily tuned by changing their electrical length. The filter's working principle is explained by a proposed transmission-line model. We designed and fabricated a passband filter centered at 0.9 THz on a 10-𝜇m silicon-membrane substrate and compared measurement results between 0.5 THz and 1.1 THz to electromagnetic simulations, showing excellent agreement in both 𝑆 11 and 𝑆 21 . The measured passband has an insertion loss of 7 dB and a 3-dB bandwidth of 31%. Overall, the proposed filter design has good performance while having a simple design procedure.

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“…Since the separation of contiguous resonators is much smaller than the wavelength, the excitation of the odd coplanar-stripline mode can be neglected [26]. Higher-order modes in the PGL decay rapidly, similarly to the Goubau line's [27], [28], and therefore were also neglected. Naturally, the line feeding the filter was modeled as a PGL with and .…”

Section: A Transmission-line Modelmentioning

confidence: 99%

Capacitively-coupled resonators for terahertz planar-Goubau-line filters

Cabello-Sanchez¹,

Drakinskiy²,

Stake³

et al. 2022

Preprint

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Low-loss planar Goubau lines show promising potential for terahertz applications. However, a single-wire waveguide exhibits less design freedom than standard multi-conductor lines, which is a significant constraint for realizing standard components. Existing filters for planar Goubau line lack clear design procedures preventing the synthesis of an arbitrary filter response. In this work, we present a design for a bandpass/bandstop filter for planar Goubau line by periodically loading the line with capacitively coupled ∕2 resonators, which can be easily tuned by changing their electrical length. The filter's working principle is explained by a proposed transmission-line model. We designed and fabricated a passband filter centered at 0.9 THz on a 10-m silicon-membrane substrate and compared measurement results between 0.5 THz and 1.1 THz to electromagnetic simulations, showing excellent agreement in both 11 and 21 . The measured passband has an insertion loss of 7 dB and a 3-dB bandwidth of 31%. Overall, the proposed filter design has good performance while having a simple design procedure.

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Propagation modes on a dielectric coated wire

Cited by 13 publications

References 7 publications

Effect of a dielectric coating on terahertz surface plasmon polaritons on metal wires

Effect of a dielectric coating on terahertz surface plasmon polaritons on metal wires

Capacitively-Coupled Resonators for Terahertz Planar-Goubau-Line Filters

Capacitively-coupled resonators for terahertz planar-Goubau-line filters

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