Nowadays, the terahertz (THz) pulse sources based on time domain spectroscopy have been marked as a well-established tool for a wide variety of applications. In many imaging applications, including industrial inspection and medical diagnosis, THz radiation is increasingly used since most materials are transparent in the THz range. However, one challenge in imaging of samples with strong THz attenuation is the typically low average power of pulsed THz sources. Furthermore, THz imaging systems with low repetition rates limit the image acquisition speed. Our group tries to circumvent these issues by developing new generation of high-power, high-repetition rate THz sources. Using these sources, we can perform through-wall THz imaging with higher signal to noise ratio of the image compered to low-power industrial setups. Besides THz imaging, our sources allow us to study material properties and investigate dynamics of various phenomena in semiconductors and aqueous solutions. In particular, water-based solutions are challenging due to the strong absorption of THz waves.