BIOLOGICAL APPLICATIONS OF TERAHERTZ TIME-DOMAIN ATTENUATED TOTAL REFLECTION SPECTROSCOPY

2022-8-25
Gelgeç, Melis
In this thesis, a Terahertz Attenuated Total Reflection Time Domain Spectroscopy (THz ATR-TDS) system was constructed to measure biological media. The constructed system driven by a Yb:doped mode-locked fiber laser had a limited bandwidth of about 0.3 THz. This bandwidth limited the analysis of various samples in the frequency domain. To overcome this limitation a method was developed so that the samples can be analyzed in the time-domain. Oral soft tissue samples collected were used in order to demonstrate that the THz ATR-TDS signals of the samples can be simulated using Inverse Fourier Transformation after analyzing the reference signals obtained without samples. Here, the refractive index of the soft tissue samples are estimated and used to model the frequency domain reference measurement after which the time-domain signals are obtained. The THz ATR-TDS measurements obtained from collected oral tissue samples are compared to simulated data and are shown to be in well agreement. 5 different types of oral tissue samples sliced to lay flat on the ATR prism surface provided by the Faculty of Dentistry of Ankara University in Ankara, Turkey were used in this study. Due to the very high percentage of water contained in the biological samples, the refractive index of the all biological samples was assumed as 1.3818±0.0049i in the spectral measurement range of the constructed system. Possible differences between this value and the actual value of the refractive indexes of the different samples are shown to be very small. Careful analysis of these differences can lead to a better estimation of the refractive index of the biological medium

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Citation Formats
M. Gelgeç, “BIOLOGICAL APPLICATIONS OF TERAHERTZ TIME-DOMAIN ATTENUATED TOTAL REFLECTION SPECTROSCOPY,” M.S. - Master of Science, Middle East Technical University, 2022.