Last Updated: July 2010
© 2008 Victor M. Bright. All Rights Reserved.
| Multidisciplinary Engineering Micro-Systems Group Mechanical Engineering: University of Colorado at Boulder |
|
Micro Cryogenic Coolers (MCC) for Terahertz Imagers Utilizing Superconducting Hot Electron Bolometers PIs: Yung-Cheng Lee, Victor M. Bright, Ray Radebaugh (NIST), Eyal Gerecht (NIST), and James C. Booth (NIST) Project field/specialty: High compression ratio MEMS compressor technology Project Description: Imaging at terahertz frequencies (defined roughly as 300 GHz - 3 THz) has a number of important military and homeland security applications, such as remote sensing of chemical and biological agents or concealed weapons detection. Because of their shorter wavelengths, THz radiation (T-rays) offers high spatial resolution for imaging through clothing or tissue. For high spectral resolution, heterodyne detectors are necessary, and consist of a mixer and a local oscillator (LO). Mixers based on high temperature superconductor hot-electron bolometers (HTS HEBs) operated at cryogenic temperatures, e.g. 70 K, offer lower noise temperatures than room-temperature Schottky diode technology, and require substantially less LO power. For example, a focal plane array with 18x18 pixels based on Schottky diodes will require more than 3W of LO power (at roughly 1 THz) whereas similar array based on HTS HEB elements will require less than 30 mW. A source to supply 3W at 1THz simply does not exist today. In order to provide the LO power for the Schottky diode mixers, or small arrays of them, FIR lasers are required, which are large, expensive, difficult to operate, and certainly not portable. For the HTS HEB devices, one can use recently-developed solid state LO sources, which can be made portable, and which are also cheaper. The LO power reduction that is achievable using HTS HEB technology represents a performance increase of 100x, and makes portable detectors and arrays possible, which simply cannot be done with any competing technology. As impressive as this performance improvement is, the reason that nobody has pushed HTS HEB technology to this point is because the HTS devices require a cryocooler to operate, which makes the approach much less attractive from the portability standpoint, if one has no choice but to use a conventional cryocooler. Therefore, the development of the proposed MCC and its integration with HTS HEB's are the enabling technologies for dramatically advancing the state-of-the-art in portable THz imagers and spectrometers for important military and homeland security applications. Funding Source: Defense Advanced Research Projects Agency (DARPA)
|
|
Last Updated: July 2010 |