High-field multi-cycle terahertz emission from axially cut β-BBO crystals reaching several hundred kV/cm

We report efficient generation of high-field multi-cycle terahertz (THz) radiation from optical rectification (OR) in axially cut β-barium borate (β-BBO) crystals driven by an 800 nm femtosecond laser. Both b-cut and c-cut crystals produce coherent THz waveforms featuring two narrowband components centered near 10 THz and 14 THz, with weaker sidebands extending up to 25 THz. At a pump power of 3.95 W, the b-cut crystal delivers 34 µW of THz power and a focused peak field of 355 kV/cm, while the thinner c-cut crystal achieves comparable output and a higher peak field of 390 kV/cm. The high-field strength, experimental simplicity, and high scalability potential make axially cut β-BBO a compact and robust solid-state source for driving strong-field dynamics and fundamental excitations in the 5-15 THz range.