Exceptionally high THz energy densities generated from organic crystals pumped with mid-infrared pulses

Optical Parametric Chirped-Pulse Amplification (OPCPA) is an emerging laser technology, providing a flexibility in operating wavelengths and power upscaling. Here, we investigate THz generation in organic crystals (DAST) by optical rectification (OR) of intense Mid-Infrared (MIR) pulses. The broadband spectrum exceeds several octaves when pumped by 100 fs, 3.9 μm OPCPA pulses. We report on an extraordinarily high THz energy density of 3.1 mJ/cm $^{\mathbf {2}}$ and crystal damage threshold $ {>}150$ mJ/cm $^{\mathbf {2}}$.