Cavity-Enhanced THz Generation via Optical Rectification of Ytterbium Ultrafast Lasers

High-repetition-rate, high-power terahertz (THz) pulse generation is essential for a wide range of applications, including time-domain spectroscopy, imaging, and materials characterization [1]. These applications demand THz sources that combine high average power, broad bandwidth, and compact setups. Most common THz generation methods, such as photoconductive antennas and optical rectification (OR) in nonlinear crystals, often struggle with power scalability and efficiency at multi-MHz repetition rates. In particular, as repetition rates approach hundreds of MHz, the limited pulse energy available from conventional near-infrared ultrafast lasers affects the conversion efficiency of OR-based THz sources. Recently, OR THz generation inside an active laser cavity showed interesting results [2]. On the other hand, passive enhancement cavities (ECs) - traditionally exploited for frequency upconversion experiments - represent a promising alternative approach for OR, offering high intracavity power levels achievable with widely available laser systems. Figure 1 (a) shows a simplified schematic setup for cavity-enhanced THz generation.