The spatial features of a subwavelength terahertz source are not accessible using time-integrated knife-edge (KE) techniques due to the nonseparable space-time nature of the radiated field and to systematic modifications induced by the blade itself. We show that by combining KE with a time-resolved electrooptical sampling, the space-time coupling can be addressed and the source field profile can be exactly reconstructed. Index Terms-Phase-sensitive field characterization, spatiotemporal field characterization, subwavelength sources, terahertz (THz) sources. I. INTRODUCTION T ERAHERTZ (THz) imaging has been the subject of intense research efforts in the last few years, owing to the recognized THz spectroscopic capabilities in material analysis [1]-[5]. The long wavelengths associated with THz radia
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