Novel T-ray Liquid Spectroscopy via Double Modulated Differential Time-Domain Spectroscopy

Liquid water absorption is one of the most enduring problems facing THz imaging and spectroscopy in biomedical applications. The absorption coefficient for liquid water shows a very high THz absorption, 200 cm^-1 at 1 THz (Mickan et al., 2004). This strong absorption is a big hurdle for T-ray spectroscopy and imaging of liquid or even wet samples (Zhang, 2002). This paper proposes a novel method for parameter extraction of a liquid, using a double modulated differential time-domain spectroscopy (DTDS) technique with dual-thickness measurement. The proposed technique improves on the previous work by replacing the required sample dithering technique (Mickan et al., 2004) with a rotating spinning wheel resulting in an improved noise performance up to two orders of magnitude.