Terahertz communications offers great potential for high-data-rate communications over short distances. But the 2-to-3-THz frequency range has long been considered a "terahertz gap" region: too high for purely electronic devices and too low for photonic devices. Fortunately, a multinational research team has designed, fabricated, and tested an all-solid-state, frequency-agile signal source that can generate more than 1 W output power from 2.48 to 2.75 THz. The frequency-multiplied signal source is driven by a W-band frequency synthesizer followed by a power amplifier capable of delivering 350 to 450 mW (+25.5 to +26.5 dBm) output power and a cascade of three balanced frequency triplers. The first-stage tripler is based on four power-combined, GaAs Schottky diode devices while the second stage uses two four-anode GaAs devices. The output tripler is a single-stage device on a thin GaAs membrane.
The researchers used the Advanced Design System (ADS) simulation software from Agilent Technologies to predict the performance of the terahertz frequency multipliers. Once the terahertz chip was fabricated, it was mounted on the bottom half of a waveguide block, and then characterized with the use of specialized test equipment. Power measurements were performed with a VDI-Erickson PM4 power meter.
The researchers found close agreement between their simulated results and the actual measured results. To the researchers' knowledge, this is the first reported instance of an electronically tunable solid-state source in the 2.4-to-2.7-THz range. See "Design and Characterization of a Room Temperature All-Solid-State Electronic Source Tunable From 2.48 to 2.75 THz," IEEE Transactions on Terahertz Science and Technology, Vol. 2, No. 2, March 2012, p. 177.