Simulations of the generation of broadband signals from DC to 100 THz by photomixing in laser-assisted field emission

Photomixing in laser-assisted field emission is simulated using (1) the method of moments to determine the optical fields induced at the tip by the radiation from two lasers, (2) density-functional theory with Floquet methods to determine the effect of these optical fields on the field emission current, and (3) the Drude model with a method first described by Sommerfeld to determine propagation of the current at the difference frequency throughout the length of the metal tip. For metals with high work functions such as tungsten, the magnitude of the current at the difference frequency varies slowly as this frequency is increased up to a roll-off at approximately 100 THz. For difference frequencies up to approximately 100 GHz this current could be carried out of the field emission tube by transmission lines, and at higher frequencies the tip may be used as a long-wire travelling wave antenna to transmit the signal out of the tube.