Comparison of three different methods for coupling of microwave and terahertz signals generated by resonant laser-assisted field emission

Photomixing in resonant laser-assisted field emission can cause the emitted current to oscillate at frequencies from de to over 100 THz, and thus shows promise for new ultrawide band devices. The signal occurs at the apex of the emitter, and we consider three methods for coupling this signal to an external load while avoiding the effects of dispersion of the bunched electron beam and the large series beam impedance (approximate to1 G Omega). These methods are use of (1) a tapered Goubau transmission line, (2) a dielectric transmission line, and (3) traveling-wave log-periodic zigzag antennas. We conclude that each of these methods could give an output power of 100 pW with an oscillating tunneling current of 1 muA at 10 THz. The output power is proportional to the square of the current for 100 muW with 1 mA. (C) 2001 American Vacuum Society.