A device and method for emitting electrons by a field effect. The device (10) includes a vacuum chamber (12) including a tip (14) having an end (18) and forming a cold cathode, an extracting anode (16), components adapted for generating a potential difference between the tip (14) and the anode (16); an electromagnetic wave source (22) outside the chamber (12); a system (24) for forwarding the electromagnetic wave emitted by the electromagnetic wave source from the outside to the inside of the chamber as far as the vicinity of the tip (14); a system (26) for focusing the electromagnetic wave, laid out inside the chamber (12); and a system (28) for aligning the electromagnetic wave outside the chamber and adapted for allowing alignment of the electromagnetic wave focused by the focusing system on the end of the tip.