The terahertz optical properties of composites with poly vinyl chloride (PVC) nanofibers and polypropylene (PP) were investigated. To evaluate the influence of PVC content, we measured the composites under conditions where the content of PVC nanofibers was controlled. We found that the refractive indices increase with the decrease of PVC nanofiber content. We also found that highly aligned PVC nanofibers bring birefringence to the composites. The proposed PVC-PP composites are promising materials for terahertz optics.
Significance: A new concept of a biotissue phantom for terahertz (THz) biomedical applications is needed for reliable and long-term usage.
Aim: We aimed to develop a new type of biotissue phantom without water content and with controllable THz optical properties by applying graphite powders into a polyvinyl chloride plastisol (PVCP) matrix and to give a numerical description to the THz optical properties of the phantoms using the Bruggeman model (BM) of the effective medium theory (EMT).
Approach: The THz optical properties of graphite and the PVCP matrix were measured using THz time-domain spectroscopy, which works in the frequency range from 0.1 to 1 THz. Two phantoms with 10% and 12.5% graphite were fabricated to evaluate the feasibility of describing phantoms using the EMT. The EMT then was used to determine the concentration of graphite required to mimic the THz optical properties of human cancerous and healthy oral tissue.
Results: The phantom with 16.7% of graphite has the similar THz optical properties as human cancerous oral tissue in the frequency range of 0.2 to 0.7 THz. The THz optical properties of the phantom with 21.9% of graphite are close to those of human healthy oral tissue in the bandwidth from 0.6 to 0.8 THz. Both the refractive index and absorption coefficient of the samples increase with an increase of graphite concentration. The BM of the EMT was used as the numerical model to describe the THz optical properties of the phantoms. The relative error of the BM for the refractive index estimation and the absorption coefficient is up to 4% and 8%, respectively.
Conclusions: A water-free biotissue phantom that mimics the THz optical properties of human cancerous oral tissue was developed. With 21.9% of graphite, the phantom also mimics human healthy oral tissue in a narrow frequency range. The BM proved to be a suitable numerical model of the phantom.
An emission illusion device based on metamaterials with the cylindrical polar angle-dependent tensors of permittivity and permeability was proposed and analyzed. The illusion effect was numerically simulated using the finite-element method for a point source. The influence of metamaterial anisotropy and radiation source position on the illusion effect was studied.
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