Numerical method based on transfer function for eliminating water vapor noise from terahertz spectra.

Area of Science:

• Spectroscopy
• Atmospheric Science
• Materials Science

Background:

• Water vapor in the atmosphere introduces significant noise into terahertz (THz) time-domain spectroscopy.
• This noise compromises the accuracy of extracted optical parameters, hindering material analysis.

Purpose of the Study:

• To develop and validate a numerical method for effectively eliminating water vapor noise from THz spectra.
• To improve the precision of optical parameter extraction in THz spectroscopy under varying humidity conditions.

Main Methods:

• Simulated water vapor absorption and refractive index spectra using the Van Vleck-Weisskopf function and HITRAN database.
• Incorporated the continuum effect of water vapor and calculated theoretical transfer functions for different humidity levels.
• Applied the developed numerical method to denoise THz spectra of a Lacidipine sample (0.5-1.8 THz).

Main Results:

• The numerical method successfully reduced water vapor noise in THz spectra.
• Optical parameters extracted from denoised spectra closely matched those obtained in a dry nitrogen environment.
• The method demonstrated effectiveness across a continuous frequency domain of 0.5-1.8 THz.

Conclusions:

• The proposed numerical method is effective in mitigating water vapor interference in THz time-domain spectroscopy.
• This technique enhances the reliability of optical parameter measurements, crucial for material characterization.
• Accurate THz spectroscopic analysis is achievable even in the presence of atmospheric humidity.