Measurements of Modulation of the Current in a Field Emitter caused by a Laser

Abstract
Numerical simulations suggest that laser illumination of a field emitter increases the tunneling curent due to a resonant interaction in which tunneling electrons exchange quanta with the laser. Thus, a laser may be used as a gate, and a time-varying current is produced if the laser is amplitude modulated. We have measured an RF tunneling current of 0.4 nA when the tungsten tip of a sealed field emitter tube is illuminated with a laser diode that is amplitude modulated at 1 MHz, and the DC curent is 5µA. The laser diode increases the DC curent by 270 nA, which is attributed to tip heating. However, the RF current (0.4 nA) has a period less than estimates of the thermal relaxation time.