THz Generation and Interaction

TeraHertz (THz) radiation has the ability to penetrate a wide variety of non-conducting materials. It can be used to manipulate electrons in materials, such as semiconductors and so initiate and drive certain effects. Particularly, it is possible to generate ultrashort, quasi single-cycle THz pulses. With the help of such pulses, it possible to understand the functional properties of materials and devices. For example, it is possible to investigate the ultimate speed of atomic-scale switches, which is of interest for next generation information and energy storage applications.

The figure shows an artist's rendering of the emission of coherent transistion radiation (yellow) by electrons (blue) passing through a metal foil. Figure: Greg Stewart, SLAC

The single-cycle THz pulses are generated by propagating a relativistic ultrashort electron pulses through a thin metal foil. During the transition between the boundary between two different media (vacuum and metal) the electrons emit radiation in form of transition radiation. The emitted radiation becomes coherent and increases in intensity for a wavelength shorter than the length of the electron pulse. With this method, it is possible to generate THz pulses with electric fields that are comparable to that of atoms. If such pulses are focused into a material, it is possible to drive extremely nonlinear processes and transiently change the material's properties.

Relevant Publications

  • Single-cycle teraherz pulses with >0.2 V/Å field amplitudes via coherent transition radiation
    Appl. Phys. Lett. 99, 141117 (2011)
  • Intense terahertz pulses from SLAC electron beams using coherent transition radiation
    Rev. Sci. Instrum84, 022701 (2013)
  • Below gap optical absorption in GaAs driven by intense, single-cycle coherent transition radiation