Electrodynamic Response of Advanced Dielectric Materials in Broadband Frequency Range




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Reliable index or permittivity data over a broad THz frequency range is challenging to find in the existing literature for many dielectric materials commonly used in the electronics industry. In this work, two classes of dielectric material characterization techniques are introduced for different dielectric polymeric materials and a high quality single crystal perovskite to expand the current knowledge on their potential electrical or opto-electronics applications in THz frequency range. First, the non-magnetic polymeric dielectric materials measurements were made using a Fourier Transform Infrared Spectrometer from 3-75 THz. Two different analyses models were used to investigate material’s properties according to the experimental data. The first model, offresonance model, used where experimental data showed non-resonance response for materials exposing to the external electric field. In contrast, on or near lattice vibration or molecular bond resonances, the attenuation or loss of material can become large enough to cause no transmission through the sample. When this occurs, we used a resonance model in the presence of resonances where the frequency of applied electric field matches with the intrinsic frequency of atoms or molecules in materials. A high quality single crystal of Methylammonium Lead Bromide perovskite also used inside FTS and the reflection and transmission measurements were done. The experimental data showed a sharp reflectance near 1.35 THz, indicating of an isolated optical phonon reststrahlen band. It also showed another reststrahlen band arising from two overlapping optical phonon modes. In the frequency regions where fall into reststrahlen bands, the real part of permittivity has an anomalous value since there is no propagating electromagnetic wave inside the material. In contrast, in the frequencies higher than 12 THz we just saw localized molecular bond resonances and no reststrahlen band observed. The other technique we introduced was a quasi-optical millimeter-wave spectrometer for magnetic and non-magnetic material characterization. We used a high resistivity silicon to investigate and confirm the accuracy of the experimental model along with the analysis model to extract permittivity and permeability of the materials.



Dielectrics, Terahertz spectroscopy, Spectrometer, Fourier transform infrared spectroscopy, Perovskite, Millimeter wave devices