Prototype optoelectronic device for generating signals from dc to 10 GHz by resonant laser-assisted field emission

Simulations show the radiation from a laser can increase field emission cur rent by resonant photoexcitation of the electrons, and photomixing could ca use oscillations of the emitted current at frequencies from de to over 100 THz. However, earlier prototypes were Limited to operation from de to 1 MHz because of inefficient coupling of the load to the apex of the emitting ti p where the signals are generated. In the new prototype the zirconium carbi de tip and the anode are mounted on an 8 mm length of parallel wire transmi ssion line. This is a one-port device, so that external to the tube, the tr ansmission line is connected to the de bias supply via a rf choke, and to t he load via a blocking capacitor and a passive element impedance matching n etwork. Because of the small dimensions and the large value of the beam imp edance, the prototype acts as a lumped current source from de to 10 GHz. In initial testing, a pulsed laser diode is used as the radiation source with a spectrum analyzer as the load. We describe the de current-voltage charac teristics of the prototype and the techniques used to obtain subnanosecond optical pulses in order to determine the frequency response of the new prot otype. (C) 2001 American Vacuum Society.