Plasma-Generated THz-Driven Electron Emission

Mr. Benjamin Colmey, Mr. Rodrigo Paulino, Dr. David Cooke
McGill University, Montreal, Canada


We demonstrate ultrafast cold-field electron emission from a nanotip with bunch charges exceeding 100,000 electrons, using THz pulses from a laser-induced air plasma. This marks a major enhancement from earlier plasma-driven experiments, where electron emissions were aided with a bias voltage, and used 25 nJ THz pulses with field strengths of 10 kV/cm1. Our approach, utilizing 1 µJ pulses and field strengths of over 150 kV/cm produced electron energies up to 1 keV, showing good agreement with Fowler-Northeim theory and suggesting emission within a sub-cycle of the THz pulse approximately 100 fs in duration. This places plasma-generated electron emission within reach of other generation methods, which have so far demonstrated bunch charges reaching approximately 106 bunch charges2. With further improvements to the plasma generation and collimation to precisely control the spatial and temporal focusing of the THz field, we suggest the capability to generate up to 107 electrons per shot, with energies reaching into the tens of keV.