Subcycle Surface Electron Emission by Strong-Field THz Waveforms

The advent of intense THz sources opened a new era when the demonstration of the generation, acceleration and manipulation of free electrons by THz pulses is within reach [1]–[3]. THz-field-driven electron emission was predicted being confined to a single burst due to the single-cycle waveforms [4]. Here, we demonstrate the confinement of single-cycle THz-waveform-driven electron emission to one of the two half cycles and the control of the active half cycle by changing the field polarity.