کنفرانس مهندسی برق ایران

صفحه اصلی / سی و چهارمین کنفرانس بین المللی مهندسی برق

Experimental Evaluation of Humidity Effects on THz-TDS and the Resulting Improvements Using Local Dehumidification

نویسندگان :

Hossein Ghani¹ Mehdi Ahmadi-Boroujeni²

1- Sharif university of technology 2- Sharif university of technology

کلمات کلیدی :

Terahertz Spectroscopy،Water Vapor Absorption

چکیده :

Terahertz time-domain spectroscopy is often used to study the spectral fingerprints of different solid materials, and sugars are among the common test samples. One issue that repeatedly came up during our measurements was the influence of normal room humidity on the recorded spectra. Even moderate levels of water vapor introduce small absorption lines—originating from the rotational transitions of water molecules—that lower the signal quality and sometimes hide weaker features of the sample. To check how serious this problem is in practice, we measured 10% D-(+)-Sucrose pellets under two conditions: first in the usual laboratory environment (about 45% RH), and then inside a small dry-air enclosure that we added around the optical path (RH below 1%). The difference between the two cases was quite noticeable. In the dry measurements, the spectrum became much cleaner, several unwanted waterrelated ripples disappeared, and the characteristic sucrose peaks appeared more clearly—especially the one around 2.235 THz, which is almost lost in the ambient measurement. Furthermore, to verify the system’s capability in complex scenarios, we tested binary mixtures. The setup successfully resolved overlapping peaks in a Sucrose/Glucose mixture and demonstrated broadband fidelity (0.3–2.6 THz) by identifying widely spaced features in a Lactose/Fructose mixture. These observations suggest that for routine THz-TDS measurements on saccharides or similar materials, even a simple local humidity-control setup can make a significant improvement and help obtain more reliable spectra for analysis.