Enhanced spatial resolution of terahertz spectroscopy via semiconductor photoexcitation

We utilize the photoexcitation of a semiconductor material as a 'reflectivity switch' for a broadband terahertz field. We show that judicious use of this switch enables temporal characterization of the THz field with spatial resolution significantly surpassing the diffraction limit of the terahertz and provides desirable means for spatio-temporal terahertz spectroscopy. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement