Terahertz electronics: The last frontier

The terahertz gap is a roughly decade-wide spectral band geometrically centered at 1THz, for which neither conventional electronics nor room-temperature photonics is particularly well suited. This paper reviews applications that reside in the gap, mapped against the capabilities of various technologies. Lithographic scaling will deliver devices with adequate small-signal performance in the THz band, but the lack of efficient, high-power (watt-level) sources remains a significant impediment to further progress. The paper concludes with an enumeration of work still to be done, and some suggestions for how it might be done, including a recommendation not to overlook appropriately reconceived vacuum electronic devices.