Development of terahertz time-domain spectrometer based on nonlinear plasma generation

Abstract

Terahertz time-domain spectroscopy (THz-TDS) is a powerful pump-probe technique that employs ultra-short laser pulses to investigate various materials, with applications spanning medicine, security, the semiconductor industry, agriculture, and art conservation. This thesis provides complex information about the aspects of the THz-TDS and guides the reader through the development process of a THz-TDS system within the IT4Innovations laser laboratory. I describe the design, construction, optimization, and experimental demonstration of the THz-TDS system, which was developed in the frame of this thesis. I concentrate on the alignment of laser beam paths and optical components to maximize THz signal amplitude and frequency spectrum. The thesis also includes an experimental analysis of the polarization sensitivity of the ZnTe crystal in the THz-TDS detection branch. My attention is further focused on the efficient generation of THz fields using a two-color plasma. Using the nonlinear four-wave mixing approach, illustrative simulations were conducted to analyze THz pulses and their dependence on input optical field parameters. The insights gained from this work lay the foundation for future improvements to the developed THz-TDS setup, enabling the validation of simulation results and driving advancements in the diverse fields where THz-TDS finds its applications.