The generation of high field terahertz radiation and its application in terahertz nonlinear spectroscopy

Abstract

In this thesis research, I implemented a terahertz generation scheme that enables high-field near-single-cycle terahertz (THz) pulse generation via optical rectification in a LiNbO3 (LN) crystal. I also developed a method for the non reconfigurable generation of high-intensity multiple-cycle THz fields aimed to more efficiently deliver THz energy to resonant samples. A novel free-space THz-pump/THz-probe setup enabled time-resolved measurement of ultrafast nonlinear electronic responses in doped bulk semiconductor samples. The ability to spectrally and temporally resolve the response of the semiconductor sample using a THz probe allowed us to uncover both the dynamics of impact ionization and interesting phonon-plasma interactions in indium antimonide (InSb) for the first time. Nonlinear vibrational responses in LN were ob-served first in a dual THz beam setup on an integrated LN waveguide platform with optical probing to reveal the generation of terahertz second harmonic signals and also in THz transmission measurements in cooled LN where THz intensity-dependent self-phase modulation and harmonic generation were observed. An outlook and preliminary results toward implementation and observation of high-field THz-driven responses in ferroelectric materials are given in the final chapter of this thesis.