Golomb Ruler Based Discrete Frequency Multimodal Continuous Wave THz Spectroscopy System

Photonic Terahertz systems covering a broad frequency range are a versatile tool for non-destructive testing and thickness determination. The advantage of these systems to measure amplitude and phase is usually accompanied by a certain complexity of the laser source or the THz parts of the setup. A cost-effective THz system which enables a fast scan over a broad frequency range would be beneficial for many applications in the THz regime. We build a system with standard telecommunication components to accomplish a frequency scan on discrete frequencies over a broad frequency range, which is usually not feasible with non-tunable monolithic diode lasers. This paper describes the main considerations for this setup and shows a proof of principle operation, as well as the requirements for upscaling the system to wider frequencies ranges and more emission lines. It is shown that with 5 diode lasers we were able to generate 10 discrete emission lines in the frequency range from 50GHz to 1170GHz. The system has the potential to accomplish high scanning speeds with no tunable elements.