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Innovative Technologies for High Power Amplification at THz frequencies



PROPOSALS ACCEPTED: Phase I and DP2. Please see the 16.2 DoD Program Solicitation and the DARPA 16.2 Direct to Phase II Instructions for DP2 requirements and proposal instructions.

TECHNOLOGY AREA(S): Electronics, Sensors

OBJECTIVE: Investigate and demonstrate an innovative and radical approach capable of revolutionizing technologies for high power amplification at terahertz (THz) frequencies.

DESCRIPTION: Vacuum electronic and solid state high power amplifiers are important technologies for a wide range of military, civilian, and commercial applications. Vacuum electronic amplifiers are based on electron beam transport in vacuum and are capable of high power amplification (gain over 40 dB), output power in the kW range, wide bandwidth (multi-octave), high reliability (100,000 hours), high efficiency (up to 90% with depressed collector), high radiation tolerance, and efficient heat dissipation. Solid state amplifier technologies are based on electron beam transport in semiconductors and tend to have higher reliability (one million hours), but with reduced output power in the range of tens to hundreds of watts and efficiency as high as 40% at microwave frequencies and below. Solid state technologies also exhibit less efficient heat dissipation that contributes to increased system size, weight, and power. Significant progress continues to be demonstrated in both technologies towards higher operating frequencies, bandwidth, and efficiency, although vacuum electronic devices still maintain an edge in applications requiring high power and efficiency at the highest frequencies.

The worldwide availability and proliferation of inexpensive, high power commercial amplifiers and sources has made the electromagnetic spectrum crowded and contested in the RF and microwave regions. The wealth of technical advantages offered by operating at higher frequencies, most notably the wide bandwidths available, are pushing both commercial and DoD solid-state and vacuum electron devices into the millimeter wave (mm-wave) region and beyond. However, pushing device operation to THz frequencies results in significant degradation in performance as the device dimensions decrease proportionally. For vacuum electronic amplifiers, the performance degradation is due to the constrained electron beam that must pass through much reduced interaction structures, as well as the challenging manufacturing and alignment tolerances. Similarly, solid state amplifier technologies suffer scaling challenges of their own that significantly limit their performance.

Researchers have demonstrated vacuum electronic amplifiers operating at 850 GHz with output power above 50 mW, 15 dB gain, and 11 GHz of bandwidth; and solid state amplifiers operating at 1 THz with output power to several milliwatts, 10 dB gain, and 90 GHz of bandwidth. However, the approaches demonstrated for both technologies are reaching their physical limits at THz frequencies. DARPA is seeking radical and innovative new approaches to fundamentally challenge the limitations imposed on power amplifier technologies at THz frequencies. At a minimum this approach will enable and enable, at the minimum, 1 W output power, 10 dB gain, 10% bandwidth, 50% power efficiency, and predicted reliability of one million hours; all in a reduced form factor for a single amplifier device. The proposed solution will provide technological advantage to military and commercial systems through increased accessibility to the regions of the electromagnetic spectrum that currently are unexplored.

The proposed approach must address all aspects of amplifier technology, including power supply and thermal management, necessary to demonstrate capabilities for high performance in a compact form factor at operating frequencies beyond 1 THz. Proposals must identify risks associated with the proposed innovative approach and present a thorough risk mitigation plan.

PHASE I: Demonstrate the feasibility of an innovative device concept capable of high power amplification enabling, at a minimum, operation at 1 THz with 1 W output power, 10 dB gain, 10% bandwidth, 50% power efficiency, and predicted reliability of one million hours from a single, compact device. Proposers will develop the initial concept design, identify key elements of the technology that will enable high performance, and perform complete analysis of the design using full-wave electromagnetic modeling and simulation. Deliverables will include a Phase I final report including a detailed plan for demonstrating a hardware prototype that can meet the performance metrics listed above.

PHASE II: Fabricate and test a single unit hardware prototype based on the Phase I concept and demonstrating the threshold performance targets. Develop and demonstrate the feasibility of concepts to extend the performance of the device to meet objective performance targets of operation at 1.5 THz with 10 W output power, 20 dB gain, 67% bandwidth, 50% power efficiency, and predicted reliability of one million hours from a single, compact device. Deliverables will include a Phase II final report including complete documentation of the prototype test results, a detailed plan for demonstrating a hardware prototype that can meet the performance metrics listed above, along with applications and prospective partners for technology transfer in Phase III.

PHASE III DUAL USE APPLICATIONS: Achieve a technology readiness level sufficient to support transition to military, civilian, and commercial applications for high power amplifiers (typically TRL 6). A successful Phase III development will demonstrate a hardware prototype based on Phase II design and meeting the objective performance targets and deliver the prototype with complete documentation to a commercial transition partner for applications in communications and sensing.


  • Defense Advanced Research Projects Agency. (2008, June). “Terahertz Electronics (THz), SOL BAA 08-54, POC Mark Rosker, DARPA/MTO.” [Online]. Available:
  • J.C. Tucek et al., “0.850 THz vacuum electronic power amplifier,” IEEE International Vacuum Electronics Conference, pp.153-154, 22-24 April 2014 (doi: 10.1109/IVEC.2014.6857535)
  • X. Mei et al., “First Demonstration of Amplification at 1 THz Using 25-nm InP High Electron Mobility Transistor Process,” IEEE Electron Device Letters, vol. 36, no. 4, pp. 327-329, April 2015 (doi: 10.1109/LED.2015.2407193)
  • Department of Defense. (2010, February). “Defense Acquisition Guidebook, Table TRL Descriptions.” [Online] Available:

KEYWORDS: Beam-wave interaction structure, beam collector, electron source, vacuum electronics

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