The Defense Advanced Projects Research Agency (DARPA) has recently posted the following request for proposals:
Terahertz Electronics
Solicitation Number: BAA08-51
Posted Date: June 13, 2008 4:00 pm EST
Current Response Date: August 29, 2008
Classification Code: A -- Research & Development
DARPA is soliciting innovative research proposals in Terahertz (THz) Electronics. Proposed research should investigate innovative approaches that enable revolutionary advances in electronic devices and integrated circuits achieving THz frequencies (at least 1.0 x 10**12 cycles per second). Specifically excluded is research that primarily results in evolutionary improvements to the existing state of practice.
http://www.darpa.mil/mto/solicitations/baa08-51/index.htmlSome quotes from the solicitation document:
"
THz Power Amplifiers. The proposer will demonstrate a power amplifier
device capable of amplifying radiation at THz frequencies. Approaches may
include, but are not limited to,
vacuum electronic devices (such as travelling
wave tubes and extended interaction klystrons) or photonic amplifiers, but
must be compact and amenable to integration with solid-state exciters. Device
performance characteristics will be consistent with the program metrics (see
section D below) taking into account predicted losses when the devices are
integrated into an assembly. Note that high-power sources (as opposed to
amplifiers) are not responsive to this BAA."
[AB2EZ comment: at 1 THz, the wavelength is 0.3 millimeters... so we are talking about some pretty small tubes :-)]
"Recently, compact, micromachined vacuum electronic devices have made it possible to produce compact and relatively high power sub-MMW sources. This technology offers one possible path to achieving efficient THz transmitters, but significant hurdles remain. The most obvious such hurdle is the complex and difficult frequency scaling required for this technology to achieve 1.0THz operation."
So... maybe someday we will see the 5th edition of the Radiotron Designers Handbook, updated with a section on THz tubes and circuits.
Best regards
Stu
P.S. I plan to submit a proposal in response to this solicitation... jointly with a colleague at NJIT... on the subject of low noise, high bandwidth (at baseband or i.f.) receivers for THz systems. Note that the sensitivity of any THz receiver will be fundamentally limited by a combination of thermal effects (as in classical radio frequency communication systems) and quantum effects (as in optical communication systems). At 1 THz frequency, if the absorbing medium (e.g., the atmosphere), through which the THz radiation is propagating, is at room temperature (293K), then the Boltzmann energy, kT, is roughly comparable to the photon energy, hf. I.e., kT ~ 4 x 10**-21 Joules, and hf ~ 6.6 x 10**-22 Joules . I hope to have a chance to combine what I have learned over the years about the design of low-noise radio frequency receivers with what I learned during my earlier research career about the design of optical frequency receivers.