Terahertz radiation is widely used for security, and produced using electronic devices. Intense lasers have brought the ability to produce intense and/or broadband Terahertz radiation through different optical processes. This intense Terahertz radiation is of interest for many applications in material science, such as material analysis in dynamic experiments, including magnetic properties, but also in accelerator machines for time tagging, electron deflection or acceleration.
Generation Mechanisms
Among the different processes to generate Terahertz radiation with intense lasers, one can use two-color filamentation, difference frequency generation, or optical rectification in organic crystals or inorganic crystals.
Two-color filamentation consists in focusing the fundamental wavelength and the second harmonic of an intense laser in air, generating a plasma with strong field distortion, ending with an intense Terahertz radiation induced by the local electronic current. The process is broadband and allows to reach up to 10THz bandwidth when using short pulses.
Optical rectification is a process induced by intense pulses propagating in dielectric materials. Due to the strong frequency difference between the laser radiation and the Terahertz radiation, the phase matching and spatial overlap conditions require either to use highly nonlinear organic crystals, or pulse front-tilted beams in inorganic crystals such as LiNbO3.
Amplitude Solutions
Amplitude proposes a broad range of solutions : for broadband Terahertz generation with two-color filamentation, ultrashort TiSa lasers have been widely used, and now post-compressed Ytterbium lasers bring increasing interest. For optical rectification in organic crystals, Ytterbium lasers are usually prefered, and for organic crystals MIR OPCPA sources are the best option.
