Data for: "Real-Time Near-Field Terahertz Imaging with Atomic Optical Fluorescence"

Terahertz (THz) near-field imaging is a flourishing discipline, with applications from fundamental studies of beam propagation to the characterisation of metameterials and waveguides. Beating the diffraction limit typically involves rastering structures or detectors with length scale shorter than the radiation wavelength; in the THz domain this has been achieved using a number of techniques including scattering tips and apertures. Alternatively, mapping THz fields onto an optical wavelength and imaging the visible light removes the requirement for scanning a local probe, speeding up image collection times. Here we report THz to optical conversion using a gas of highly excited 'Rydberg' atoms. By collecting THz-induced optical fluorescence we demonstrate a real-time image of a THz standing wave and we use well-known atomic properties to calibrate the THz field strength. The mono-atomic gas does not distort the THz field and offers the potential to immerse structures within the THz-to-optical conversion medium.