Intense THz source based on BNA organic crystal pumped at Ti:sapphire wavelength

We report on high-energy terahertz pulses by optical rectification (OR) in the organic crystal N-benzyl-2-methyl-4-nitroaniline (BNA) directly pumped by a conventional Ti:sapphire amplifier. The simple scheme provides an optical-to-terahertz conversion efficiency of 0.25% when pumped by collimated laser pulses with a duration of 50 fs and a central wavelength of 800 nm. The generated radiation spans frequencies between 0.2 and 3 THz. We measured the damage threshold, as well as the dependency of the conversion efficiency on the pump fluence, pump wavelength, and pulse duration.