Dazhen Gu
National Institute of Standards and Technology
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Featured researches published by Dazhen Gu.
Proceedings of SPIE, the International Society for Optical Engineering | 2005
Eyal Gerecht; Dazhen Gu; Sigfrid Yngvesson; Femando Rodriguez-Morales; Ric Zannoni; John Nicholson
We have achieved the first demonstration of a low-noise heterodyne array operating at a frequency above 1 THz (1.6 THz). The prototype array has three elements, consisting of NbN hot electron bolometer (HEB) detectors on silicon substrates. We use a quasi-optical design to couple the signal and local oscillator (LO) power to the detector. We also demonstrate, for the first time, how the HEB detectors can be intimately integrated in the same block with monolithic microwave integrated circuit (MMIC) IF amplifiers. Such focal plane arrays can be increased in size to a few hundred elements using the next generation fabrication architecture for compact and easy assembly. Future HEB-based focal plane arrays will make low-noise heterodyne imaging systems with high angular resolution possible from 500 GHz to several terahertz. Large low-noise HEB arrays are well suited for real-time video imaging at any frequency over the entire terahertz spectrum. This is made possible by virtue of the extremely low local oscillator power requirements of the HEB detectors (a few hundred nanowatts to a microwatt per pixel). The operating temperature is 4 to 6 K, which can be provided by a compact and mobile cryocooler system, developed as a spin-off from the space program. The terahertz HEB imager consists of a computer-controlled optical system mounted on an elevation and azimuth scanning translator which provides a two-dimensional image of the target. We present preliminary measured data at the symposium for a terahertz security system of this type.
Proceedings of SPIE, the International Society for Optical Engineering | 2006
Eyal Gerecht; Dazhen Gu; Fernando Rodriguez-Morales; Sigfrid Yngvesson
Imaging and spectroscopy at terahertz frequencies (defined roughly as 300 GHz - 3 THz) have great potential for both healthcare and homeland security applications. Terahertz frequencies correspond to energy level transitions of important molecules in biology and astrophysics. Terahertz radiation (T-rays) can penetrate clothing and, to some extent, can also penetrate biological materials, and because of their shorter wavelengths they offer higher spatial resolution than microwaves or millimeter waves. We describe the development of a novel two-dimensional scanning, passive, terahertz imaging system based on a hot electron bolometer (HEB) detector element. HEB mixers are near quantum noise limited heterodyne detectors operating over the entire terahertz spectrum. HEB devices absorb terahertz radiation up to the visible range due to the very short momentum scattering times. The terahertz imaging system consists of a front-end heterodyne detector integrated with a state-of-the-art monolithic microwave integrated-circuit low-noise amplifier (MMIC LNA) on the same mixer block. The terahertz local oscillator (LO) signal is provided by a commercial harmonic multiplier source.
Archive | 2005
Ric Zannoni; K.S. Yngvesson; Fernando Rodriguez-Morales; John Nicholson; Dazhen Gu; Eyal Gerecht
Archive | 2005
Fernando Rodriguez-Morales; Eyal Gerecht; Dazhen Gu; Richard Zannoni; Sigfrid Yngvesson; Niklas Wadefalk; John Nicholson
Microwave and Optical Technology Letters | 2010
Dazhen Gu; David K. Walter; James P. Randa
Archive | 2009
Dazhen Gu; Yan Zhuang; Sigfrid Yngvesson
Microwave and Optical Technology Letters | 2009
Dazhen Gu; Fernando Rodriguez-Morales; Sigfrid Yngvesson
Space Terahertz Technology International Symposium | 2006
Dazhen Gu; Eyal Gerecht; Fernando Rodriquez Morales; Sigfrid Yngvesson
International Symposium on Space Terahertz Technology | 2005
Dazhen Gu; Eyal Gerecht; Xin Zhao; Sigfrid Yngvesson
Archive | 2004
Eyal Gerecht; Dazhen Gu; Xin Zhao; John Nicholson; Fernando Rodriguez-Morales; Sigfrid Yngvesson