Simulations of tapered Goubau line for coupling microwave signals generated by resonant laser-assisted field emission

Abstract

Simulations of photomixing in resonant laser-assisted field emission show oscillations of the tunneling current at frequencies from dc to over 100 THz. Thus far prototype devices using this effect have been limited to operation from dc to 1 MHz because of inefficient coupling of the load to the apex of the emitting tip where the signals are generated. Goubau line, which is a broadband surface-wave transmission line, could be formed by coating the emitting tip with a dielectric. We have used the finite-difference time-domain method to model coupling with tapered Goubau line. We conclude that a power of 1 nW could be coupled to a 50 Ω load from an oscillating tunneling current of 1 μA at 10 GHz. The output power is proportional to the square of the current, and we consider methods for obtaining current oscillations of 1 mA or greater.