Exact Reconstruction of THz Sub-$\lambda$ Source Features in Knife-Edge Measurements

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 electro-optical sampling, the space-time coupling can be addressed and the source field profile can be exactly reconstructed.