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Terahertz dielectric characterisation of fibres in a time-domain spectrometer

Pacewicz Adam, Kopyt Paweł, Cuper Jerzy, Krysicki Mateusz, Salski Bartłomiej

Opto-Electronics Review

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2023

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Vol. 31, No. 2

art. no. e144596

EN

An innovative measurement setup for the dielectric characterisation of fibres in a terahertz time-domain spectrometer using an HDPE elliptical lens for coupling into the fibres has been built and validated by measurements of several different types of samples. The setup is based on a commercial all fibre-coupled terahertz time-domain spectrometer. Measurements of the effective refractive index have been conducted on polypropylene-based three-dimensional printing filaments, silica glass rods, and a polytetrafluoroethylene cord of lowered density, covering the frequency range of approximately 100 GHz to 1 THz. The theoretical part of the work includes numerical calculations performed via the finite difference eigenmode method and the characteristic equations of a uniform circular dielectric waveguide for a few guided modes, from which it is clear that primarily the fundamental mode propagates along the fibre. Details on model-based phase corrections, crucial to the accurate determination of the effective refractive index of dispersive fibres, have been presented as well.

2

Wybrane metody charakteryzacji mikrofalowej materiałów magnetycznie żyrotropowych

Pacewicz Adam

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2022

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nr 4

457--460

PL

Rezonansowe metody charakteryzacji mikrofalowej materiałów magnetycznie żyrotropowych mają potencjał, aby stać się standardem w przemyśle. Szczególnie znaczenie posiadają materiały ferrytowe, znajdujące zastosowanie w konstrukcji cyrkulatorów, izolatorów czy strojonych filtrów. W pracy zawarto podsumowanie prac nad rozwojem metod rezonansowych do charakteryzacji materiałów ferrimagnetycznych o kształcie sferycznym i planarnym, przede wszystkim szerokości linii rezonansu ferromagnetycznego i magnetyzacji nasycenia.

EN

Resonance methods for microwave characterization of magnetically gyrotropic materials have the potential to become an industry standard. Ferrite materials that are used in the construction of circulators, insulators and tuned filters are of particular importance. The paper summarizes the work on the development of resonance methods for the characterization of spherical and planar ferrimagnetic materials, especially the ferromagnetic linewidth and saturation magnetization.

3

Measurements of the responsivity of FET‐based detectors of sub‐THz radiation

Kopyt Paweł, Salski Bartłomiej, Pacewicz Adam, Zagrajek Przemysław, Marczewski Jacek

Opto-Electronics Review

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2019

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Vol. 27, No. 2

123--129

EN

This article describes a novel approach to measure responsivity of a FET-based sub-THz detector using on-wafer probes to directly feed a bare antenna-less detecting device. Thus, the approach eliminates the need to know beforehand the detector’s effective aperture, which can be a source of large variation between responsivity measurements of various FET-based detectors often cited in the literature. It seems that the presented method can be useful at making direct comparisons between responsivity of various devices (e.g., MOSFETs, HEMTs etc.). As a demonstration, the sub-THz responsivity of a pHEMT device fabricated using a commercial GaAs process has been measured in a WR-3 frequency band. Additionally, the results have been compared against data obtained using an alternative approach. The verification method consisted in integrating exactly the same device with a broad-band antenna and a carefully selected high-resistivity silicon lens and comparing its performance with that of a commercial calibrated detector based on Schottky diodes.