Noise reduction in terahertz thin film measurements using a double modulated differential technique

Abstract

Differential terahertz (THz) time-domain spectroscopy (TDS) is a technique for decreasing noise levels in THz thin film characterization experiments. Characterizing thin films in the GHz to THz range is critical for the development of fast integrated circuits and photonic systems, and is potentially applicable to biosensors and proteomics. This paper shows how the differential technique, combined with double modulation, enables the study of thin films with noise reduction over normal TDS that improves at the film gets thinner. Double modulated differential THz-TDS has enabled the characterization of films with less than 1-μm thickness.