The Terahertz Laboratories

Novel THz emitters

The photo-Dember (PD) effect is a THz emission mechanism based on ultrafast carrier transport. THz radiation is produced by illumination of a semiconductor surface by an ultrafast near infrared laser with energy above the bandgap (usually Ti:S). The strong absorption of light near the surface creates a large carrier gradient of electrons and holes, which initiates a diffusion current. Because of the different mobilities, electrons and holes spatially separate on a picosecond time scale.

In the THz laboratories group we simulated the diffusion of the carriers in combination with a theoretical analysis of the emission of a dipole under a metal sheet. We have developed an emitter that works based on diffusion currents and the suppression of dipoles under a semi-infinite metallic sheet [1, 2]. We have experimentally demonstrated the emitters using semiconductor (GaAs) substrates. This mechanism indicates a novel method of generating THz radiation that is based on the diffusion current created by ultrafast radiation but also uses the inhibition of radiation due to a metal surface. This concept gives rise to design proposals for a series of emitters, which would give similar performance to a Photo-conductive antenna, which is currently the standard THz emitter. This work is funded by EPSRC for the development of a high power THz spectrometer based on PD emitters and THz lasers.

  1. G. Klatt, et al, “Terahertz emission from lateral photo-Dember currents,” Opt. Express 18, 4939–4947 (2010).
  2. M. E. Barnes, et al., “Terahertz emission by diffusion of carriers and metal-mask dipole inhibition of radiation,” Opt. Express 20, 8898-8906 (2012)