Ultra-broadband THz time-domain spectroscopy based on organic crystals for materials testing

Terahertz (THz) spectroscopy has been established as a powerful technique to study phonon modes and charge transport mechanisms of various materials, including materials for organic electronics and photovoltaics. We report on our approach using organic crystals as THz generators and detectors for the emerging ultra-broadband THz range, extending beyond the fewTHz limit of commercial systems. By optimizing both the organic crystals and the experimental configurations, we achieved THz-wave generation and detection in a broad THz range up to 15 THz, well above the limits of the inorganic standard ZnTe crystals. Employing a compact and a relatively low-cost telecom femtosecond pump laser at 1560 nm and a high repetition rate of 100 MHz, we can achieve a dynamic range up to 80 dB with frequency components up to 20 THz at a resolution below 3 GHz. Using this system, we report on ultrabroadband THz time-domain spectroscopy and imaging of different materials interesting for optoelectronic applications.