Simulations show the radiation from a laser can increase field emission current by resonant photoexcitation of the electrons, and photomixing could cause 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 tip where the signals are generated. In the new prototype the zirconium carbide tip and the anode are mounted on an 8 mm length of parallel wire transmission line. This is a one-port device, so that external to the tube, the transmission line is connected to the de bias supply via a rf choke, and to the load via a blocking capacitor and a passive element impedance matching network. Because of the small dimensions and the large value of the beam impedance, 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 characteristics of the prototype and the techniques used to obtain subnanosecond optical pulses in order to determine the frequency response of the new prototype.