THz photogun transversely pumped by twin single-cycle pulses

Scaling the RF-photogun concept to terahertz (THz) frequencies brings several compelling advantages, including compactness, intrinsic timing between the photoemission and driving field sources, and high field gradients associated with the short THz wavelength and high breakdown threshold. These benefits, however, come at the cost of smaller dimensions and tighter tolerances which are challenging to reach in practice. Here we summarize first experiments testing the performance of a THz photogun pumped transversely by twin single-cycle THz pulses and discuss challenges facing future development of the concept.