In the absence of other qualified sources, it is the intent of the National Institute of Standards and Technology (NIST) of the Department of Commerce to acquire research support for a study on - Low Noise NbN Hot Electron Bolometer (NbN HEB) System Integration from the University of Colorado in Boulder, Colorado. A. Background: The Terahertz Technology Project in NIST's Electromagnetics Division submitted a proposal entitled, "Development of Low-Noise NbN Hot Electron Bolometer (HEB) THz Receiver Technology for Temperatures above 10 K"" in response to NASA Research Announcement NRA 00-OSS-01 of the Space Astrophysics Research and Analysis program. The proposal outlined a plan of research on the performance of extremely thin films of Niobium Nitride (NbN), as heterodyne detector elements in ultra-low noise, terahertz-frequency spectrometers. Such spectrometers are used in many NASA missions to obtain data on the chemical composition and physical properties of the Earth's atmosphere, the atmospheres of other planets, and interstellar nebulae. After a competitive evaluation of the proposal described above, NASA transferred funds to NIST to support this joint institutional study. The three institutions involved in the proposal were NIST, the University of Massachusetts and the University of Colorado. This contract to the University of Colorado is to support the final phase of the team proposal. B. SCOPE: The University of Colorado will integrate niobium nitride hot-electron-bolometers with the LO laser source and a cryocooler for demonstration of technology compatibility. The core of this research will be measurements of receiver noise temperature of NbN HEB in ambient temperature of available state-of-the-art cryocooler using a FIR laser as the LO source. C. PERIOD OF PERFORMANCE: The contract period consists of a 10-month period of performance from 6/1/2004 through 3/30/2005. D. SOLE SOURCE: NIST has determined that only the University of Colorado can perform the research described in the statement of work due to the following: I. Their capability to handle the exceptionally demanding integration of systems, based on NbN hot electorn bolometric mixers used for astronomy or remote sensing of the atmosphere and II.. Their unique testing facilities. I. The group of Dr. Albert Betz at CU has extensive experience in developing and deploying such systems. The unusual properties that make integration very challenging include: (a) Cryogenic testing: The bolometers are to operate at temperatures between 4 and 10 K (degrees above absolute zero). The test facilities therefore must provide capability to cool a sample, along with cold electronics, to temperatures in this range. Understanding the temperature dependence of the bolometer properties is critical, and near the upper end of the range, the temperature dependence can be quite strong. Therefore the test facility must be able to hold the sample at any fixed temperature within the 4-10 K operating range, to within 0.01 K. This type of cryogenic capability is typically found at research labs rather commercial electronics test services. Commercial microwave electronics suppliers typically do not test their products at cryogenic temperatures. The CU group's facilities have all necessary cryogenic capabilities, which has been verified by their research publications, and by on-site visits of NIST personnel. (b) Ultra-low microwave noise: The most important bolometer property to be tested is noise, under both DC-biased conditions and DC-biased plus terahertz driven conditions. In order to obtain meaningful results the intrinsic noise of the test facility must be low enough to avoid dominating the measurement. Typically, a noise temperature of 5 K or below, at 1 GHz, is required. This requires the use of cryogenic microwave electronics, closely integrated with the sample and cooled to the 10-15 K range. The construction and operation of such cryogenic, low-noise electronics is a highly specialized capability. The capability has been developed only at a few institutions, e.g. the National Radio Astronomy Observatory (NRAO) Charlottesville, VA, and a few universities. The CU group's facilities have all necessary low-noise microwave capabilities, which has been verified by their research publications, and by on-site visits of NIST personnel. (c) Terahertz LO source drive capability: The NASA contract requires measurements of bolometer noise under "pumped" conditions, i.e. when driven with a terahertz-frequency source, as would be the case in a heterodyne receiver. This obviously requires that the contractor have available a terahertz frequency source. The frequency range required for this contract is approximately 1- 5 THz, with at least 10 specific frequencies in this range needed, at power levels above 1 mW. This can only be provided by complex and expensive (over $ 200,000) molecular gas laser systems, which few laboratories possess. In fact, there are only two other institutions with molecular gas lasers of the required stability (see 2a (iii) below): Jet Propulsion Laboratory and Lucent Technologies. Both have made strategic decisions not to pursue work on NbN mixers because they are pursuing other technologies instead (Nb diffusion cooled mixers and GaAs 2D electron gas mixers, respectively.) This is known from direct discussions with, or professional presentations given by, the JPL and Lucent personnel involved. The CU group has flown such mobile terahertz LO source laser on an airborne platform and has additional sources in their laboratory. (d) Expertise and prior experience: It must be emphasized that the devices which require testing are experimental. Their testing absolutely requires the ability to analyze unique engineering problems arising out of the unusual cryogenic, low-noise, and high frequency properties of the devices. The only convincing way to demonstrate this ability to solve such engineering problems is through the publication of research papers describing their solution. The CU group has an enormous experience in developing detector-based systems at terahertz frequencies for astronomy and remote sensing as is evident by their long list of publications. II. The testing facilities at CU have been developed over a decade, and were specifically designed for the testing of terahertz receivers. Heterodyne receiver test capabilities at other institutions, e.g. JPL, Yale. Univ., NRAO, Harvard Center for Astrophysics (CFA), were all developed for testing of other types of detector at different frequency ranges, and would require significant modification for use with NbN HEB's at frequencies above 1.5 THz. The specific technical capabilities not available from any other source include: i. Testing capability over the continuous temperature range from 4- 10 K, with 0.01 K stability and accuracy. ii. Instrumental microwave noise below 5 K at 1 GHz, and capability to measure microwave noise with comparable instrumental noise levels over the range 0.5 - 5 GHz. iii. Ability to quasi-optically drive the sample with range 0.5 - 5 GHz. iii. Ability to quasi-optically drive the sample with range 0.5 - 5 GHz. iii. Ability to quasi-optically drive the sample with terahertz-frequency radiation, with at least 10 separate frequencies spanning the 1- 5 THz range, at power levels greater than mW, with power stability better than 1 % over an hour. Each of the capabilities described above in (a) through (c) is available at a small number of research institutions in the U.S. but none of the other institutions possess all of the capabilities or has the unique testing facilities described above except CU. In addition, CU has adapted their test capabilities to the particular requirements of NbN mixer testing. This notice may represent the only notice. See note 22.
