Use of Goubau line to couple microwave signals generated by resonant laser-assisted field emission

Simulations suggest that ultrawide band signals from DC to over 100 THz could be generated by photomixing in resonant laser-assisted field emission. However, measurements have been limited by the coupling to the apex of the emitting tip where these signals are generated. Goubau line, which is a broad-band surface-wave transmission line, could be formed by coating the emitting tip with a dielectric. We have modeled the use of Goubau line including (1) determining the coupling efficiency of the transition at the apex of the tip, (2) tapering the transmission line from the shank to the apex, and (3) horn transitions to low-impedance coaxial line at the vacuum feedthrough for the tip electrode. Our simulations suggest that a single device could provide efficient coupling over a bandwidth of two decades in frequency, and that this method is suitable for operating frequencies from 100 MHz to 10 THz.