Development of a Novel Terahertz Cross-Correlation Spectroscopy System

Terahertz (THz) spectroscopy, covering the frequency range between microwaves and infrared radiation, has historically presented significant technological challenges due to limitations in efficient generation and detection technologies. Advances in the 21st century have significantly expanded THz capabilities, particularly through the introduction of THz cross-correlation spectroscopy (THz-CCS), which leverages incoherent radiation and photomixing for generating coherent THz signals without ultrafast lasers. This thesis describes the development of a novel THz-CCS system designed for industrial environments, emphasizing cost-effectiveness, robustness, and operational simplicity. The all-fiber-based system presented utilizes fiber-coupled photoconductive antennas, a broadband amplified spontaneous emission source at telecom wavelengths, and a fiber-optic delay unit. Detailed experimental characterizations, including emitter-detector performance analysis, analysis of systematic delay errors, and evaluation of optical source stability, demonstrate the system’s capabilities. As part of this work, we introduce a novel delay-line error correction algorithm that enhances spectral accuracy by mitigating systematic optical delay errors, thereby improving the reliability of THz-CCS. Finally, we demonstrate the versatility of the developed THz-CCS system through two applications. First, we apply it to the conductivity mapping of large-area graphene layers, leveraging its broadband capabilities to characterize sheet conductivity and uniformity. Second, we apply THz-CCS to quality control of printed electronics, demonstrating its ability to monitor conductive ink properties during the printing process. These applications demonstrate the practicality of THz-CCS for industrial settings, attempting to bridge the gap between academic research and large-scale manufacturing by providing a non-contact and non-destructive solution for material characterization and process monitoring.