A compact electron source for the dielectric laser accelerator

In this work, we design and demonstrate a compact electron source that combines an integrated silicon nanotip photoemitter with a compact silicon-based electrostatic lens. The lens simultaneously accelerates electrons to 30 keV and focuses the resulting beam to a 0.4 μm (RMS) beam diameter with 62 pm-rad normalized emittance at a distance of 20 mm from the cathode. The compact nature of this lens provides a compelling source for dielectric laser accelerator (DLA) beamlines, ultrafast electron diffraction, or ultrafast electron microscopy. Driven by a 220 fs, 1960 nm pulsed laser beam, electron currents up to 28 electrons/pulse at 100 kHz are demonstrated. The electron bunch length is 540 ± 50 fs for photocurrents of