Time domain terahertz spectroscopy: construction of the setup and application in analysis of active pharmaceutical ingredients

Aytekin, Yusuf Samet
The purpose of this thesis is to build a homemade Terahertz (THz) Time Domain Spectrometer and analysis of Active Pharmaceutical Ingredients (API) by using the built THz-TDS spectrometer. Several configurations of THz-TDS system were setup and tested in order to optimise experimental parameters. These set-ups can be grouped into two; antenna-antenna and antenna-crystal. In antenna-antenna systems, photoconductive antenna (PCA)and interdigital photoconductive antenna (iPCA) were employed and both were tried for generation and detection of THz field. None of the two set-ups resulted in a good signal-to-noise ratio (SNR) or dynamical range (DR) both in time domain and frequency domain. In antenna-crystal systems, both PCA and iPCA were employed for terahertz generation and 500 µm ZnTe crystal was used for electro-optic sampling. In this case, iPCA-crystal combination gave the best SNR and larger dynamical range. Once the generation and detection types were determined, optimisation studies were carried out to measure optical properties of APIs. A modelocked oscillator Ti:Sapphire laser with central wavelength of 800 nm, repetition rate of 80 MHz, pulse duration of 80 fs and output power of ~550 mW was used as the laser source to generate and detect THz radiation. The final system has 3 THz bandwitdh and > 105 SNR. Afterwards, several APIs of common drugs were analysed by using both the optimised homemade THz-TDS setup and FT-THz system. The results have shown that each API had a characteristic THz spectrum, that can be used for the identification and characterisation of API.


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Terahertz time-domain spectroscopy systems were developed and used for the anaylsis and characterization of various materials. By using ultra-fast Ti:Sapphire and Er-doped fiber lasers, terahertz time-domain spectrometers of different configurations were constructed and tested. To increase the accuracy and sensitivity of the measurements, the systems were optimized for spectroscopic analysis. MBE grown nominally undoped epitaxial GaAs samples were used for the spectroscopic measurements. These samples were ...
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In this study we present the direct terahertz timedomain spectroscopic measurement of CVD-grown multilayer graphene (MLG) on PVC substrate with an electrically tunable Fermi level. In a configuration consisting MLG and injected organic dopant, the transmitted intensity loss of terahertz radiation was observed with an applied voltage between 0 and 3.5 V.We showed that MLG on PVC devices provided approximately 100 % modulation between 0.2 and 1.5 THz at preferentially low operation voltage of ca. 3V. The obse...
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Citation Formats
Y. S. Aytekin, “Time domain terahertz spectroscopy: construction of the setup and application in analysis of active pharmaceutical ingredients,” M.S. - Master of Science, Middle East Technical University, 2016.