Abstract-Experimental measurement of temperature-dependent sellmeier coefficients and thermo-optic coefficients of polymers in terahertz spectral range

Muhammad Mumtaz, M.Ahsan, Mahmood, Sabih D. Khan, M. Aslam Zia, Mushtaq Ahmed, Izhar Ahmad,

 
https://www.sciencedirect.com/science/article/pii/S0925346719301661

Terahertz time-domain spectroscopy has been used to measure the temperature-dependent absorption coefficients and refractive indices of different polymers in 0.2–1.8 THz spectral frequency. The coefficients of temperature-dependent Sellmeier equation for all these polymers have also been evaluated by statistical fitting the measured data, which will be helpful for the evaluation of dispersion properties of the material. Additionally, the thermo-optic coefficients have been evaluated to be the range of $-1.230\times {10}^{-4}$ to $-2.50\times {10}^{-4}$ K−1 for 298–373 K. This data would be helpful for the applications of polymers as THz-waveguide and other temperature sensitive devices. These results provide a temperature-dependent database of optical properties of different polymers for their efficient utilization in THz technology.

Abstract-Investigation of the optical and conductive properties of antimony-doped titanium dioxide using terahertz time-domain spectroscopy

M Mumtaz, M Ahsan Mahmood, Rashad Rashid, Mushtaq Ahmed, M Aslam Zia, Izhar Ahmad

http://iopscience.iop.org/article/10.1088/1612-202X/aad87d

The refractive index, absorption coefficient, dielectric constant and conductivity of titanium dioxide at different doping concentrations of antimony (Sb) have been investigated using the non-contact and damage-free technique of terahertz time-domain spectroscopy. Simple effective medium theory has been applied to composite samples to extract the dielectric and conductive response in the range of 0.2–1.2 THz. The frequency-dependent values of these parameters are observed to increase with doping concentration and also with calcination temperature. Drude–Smith model fitting with the measured conductivity curves reveals that back-scattering is the major conductivity mechanism.

Abstract-Investigation of Dielectric Properties of Polymers and their Discrimination Using Terahertz Time-Domain Spectroscopy with Principal Component Analysis

Muhammad Mumtaz, Ahsan Mahmood, Sabih D. Khan, M. Aslam Zia, Mushtaq Ahmed, and Izhar Ahmad

https://www.osapublishing.org/as/abstract.cfm?uri=as-71-3-456&origin=search

Polymers are among the most commonly used materials in our everyday life. They are generally transparent to terahertz (THz) radiation, but are quite difficult to differentiate using optical techniques as few or no characteristic features exist in the spectral range of <2.0 THz for small and portable radiation systems. In this work, we report experimental measurement of refractive indices and absorption coefficients of styrene acrylonitrile (SAN) and Bakelite in the spectral range of 0.2–2.0 THz for the first time. Additionally, we demonstrate that by combining principle component analysis (PCA) with THz time-domain spectroscopy one can differentiate such polymers. In this analysis, the first three principle components PC1, PC2, and PC3 depict >94% variance with a distribution of 72.45%, 11.52%, and 9.38%, respectively.