Subwavelength Video-Rate Terahertz Carrier Microscopy

Ultrafast Optical-Pump-Terahertz-Probe (OPTP) spectroscopy has been used for decades to analyze the carrier dynamics of semiconductors, becoming instrumental in developing new applications in electronics and material physics. The interest in this methodology relates to its suitability for optically opaque samples [1] . Besides, the low energy of THz photons results in a classical interaction with photo-carriers. When carriers are photo-excited on the surface of the material, the reflectivity and transmission of the sample are modified by the conductivity transient induced by hot-carriers. In OPTP, such a change can be related to several physical properties, such as semiconductor doping, defects, and surface recombination centers [2] .