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71.  
Type II superlattice enables high operating temperature
Type II superlattice enables high operating temperature
SPIE Newsroom - October 25, 2011
Currently, commercial technologies for MWIR detection and imaging are based on indium antimonide (InSb), mercury cadmium telluride (HgCdTe or MCT), or quantum-well IR photodetector systems. However, these materials are fundamentally limited. We recently developed a novel variant of Type-II superlattices, the M-structure superlattice with large effective mass and tunability of band-edge energies. This M-structure has been incorporated in a novel photodiode architecture for operation at high temperatures. A focal plane array based on this new material and detector architecture with improved electrical performance provides mid-wavelength-IR imaging of a human being at 170K. ... [read more]
 
72.  
New Generation of Superlattice Camera Add More Color to Night Vision
New Generation of Superlattice Camera Add More Color to Night Vision
McCormick News Article - October 19, 2011
Recent breakthroughs have enabled scientists from the Northwestern University’s Center for Quantum Devices to build cameras that can see more than one optical waveband or “color” in the dark. The semiconducting material used in the cameras – called type-II superlattices – can be tuned to absorb a wide range of infrared wavelengths, and now, a number of distinct infrared bands at the same time. The idea of capturing light simultaneously at different wavelengths isn’t new. Digital cameras in the visible spectrum are commonly equipped with detectors that sense red, green, and blue light to replicate a vast majority of colors perceived by the human eye. Multi-color detection in the infrared spectrum, however, offers unique functionalities beyond color representation. The resonant frequencies of compounds can often be found in this spectral range, which means that chemical spectroscopy can be relayed in images real-time. Razeghi’s group engineered the detection energies on the cameras to be extremely narrow, close to one-tenth of an electron volt, in what is known as the long-wave infrared window. Creating the cameras was difficult, however, because the light-absorbing layers are prone to parasitic effects. Furthermore, the detectors were designed to be stacked one on top of another, which provided spatially coincident pixel registration but added significantly to the growth and fabrication challenges. Nevertheless, a dual-band long-wave infrared 320-by-256 sized type-II superlattice camera was demonstrated for the first time in the world, the results of which were published in the July 2011 issue of Optics Letters. ... [read more]
 
73.  
Razeghi and group develop small, narrowband room-temperature terahertz source
Razeghi and group develop small, narrowband room-temperature terahertz source
Laser Focus World magazine - October 2, 2011
A chip containing two mid-IR quantum-cascade (QC) lasers is at the heart of a small room-temperature terahertz-radiation source developed by researchers at Northwestern University.1 Using intracavity difference-frequency generation, the chip emits 4 THz radiation with a linewidth of only 6.6 GHz and an output power of up to 8.5 μW. The research was headed by a scientist well-known for her work on QC lasers -- Manijeh Razeghi, a professor at Northwestern University's McCormick School of Engineering and Applied Science. As is well-known to Laser Focus World readers, terahertz radiation can be used for security screening, terahertz-absorption spectroscopy for detecting biological and chemical compounds, and, through mixing, detection of weak terahertz signals from deep space. Coherent terahertz radiation has historically been very difficult to generate, and the search for an easy-to-use, compact source continues today. Existing terahertz sources are large, multi-component systems that may require complex vacuum electronics, external pump lasers, and/or cryogenic cooling. A single-component device without any of these limitations is highly desirable for next-generation terahertz systems. ... [read more]
 
74.  
Researchers Realize High-Power, Narrowband Terahertz Source at Room Temperature
Researchers Realize High-Power, Narrowband Terahertz Source at Room Temperature
McCormick News Article - September 27, 2011
Researchers at Northwestern University have developed a simpler way to generate single-chip terahertz radiation, a discovery that could soon allow for more rapid security screening, border protection, high sensitivity biological/chemical analysis, agricultural inspection, and astronomical applications. Coherent terahertz radiation has historically been very difficult to generate, and the search for an easy-to-use, compact source continues today. One possible avenue toward achieving a robust single component terahertz source is to create and mix two mid-infrared laser beams within a single semiconductor chip in the presence of a giant nonlinearity. The researchers at the CQD have incorporated a novel dual-wavelength diffraction grating within the laser cavity to create single mode (narrow spectrum) mid-infrared sources, which in turn has led to very narrow linewidth terahertz emission near 4 terahertz. The initial device yielding powers of 10 microwatts, but Razeghi said her group will continue in hopes of reaching higher power levels: “Theory says that it is possible, and we have all of the tools necessary to realize this potential.” ... [read more]
 
75.  
FlightGlobal Engineering Student Of The Year: Where are they Now?
FlightGlobal Engineering Student Of The Year: Where are they Now?
FlightGlobal Magazine - September 15, 2011
Bayram, a graduate student at the Center for Quantum Devices at Northwestern University in Ilinois, shared the 2009 award with Michael Grant after his work developing semiconductor-based energy-efficient high performance optoelectronic device technologies impressed the judges. Originally from Turkey, Bayram came to Northwestern after graduating with a batchelor of science degree in electrical engineering from Bilkent University in Ankara, and chose the centre because of the reputation of its director, Manijeh Razeghi, “a world-leading authority” in that field, he says. Bayram now works as a research scientist at IBM TJ Watson Research Centre at Yorktown Heights, New York. The Boeing award, he says, “has brought world-wide exposure to my work and enabled broadening my vision. After the Boeing award, I have established strong collaborations including those with Boeing, Dow Chemical, and IBM extending my contributions into terahertz wavelength technologies.” ... [read more]
 
76.  
Efficient laser arrays for infrared spectroscopy
Efficient laser arrays for infrared spectroscopy
SPIE Newsroom - June 13, 2011
All molecules absorb infrared radiation at characteristic frequencies, with most substances preferring the mid-infrared band (roughly, the 3–16μm wavelength range). Hence, infrared spectroscopy can be applied to the study and identification of chemicals. Recently, there have been tremendous improvements in mid-infrared QCL technology in terms of output power and efficiency. In addition, we continue to explore possibilities of combining high power capability with tunable single mode (single wavelength) devices since a laser array with these characteristics is particularly attractive for chemical sensing applications. We have recently demonstrated the first DFB QCL array working in continuous-wave mode at room temperature that covers a wide spectral range from 4.5 to 4.7μm. This chip can deliver up to 150mW continuous-wave output power with low fidelity thermal packaging (see Figure). ... [read more]
 
77.  
CQD ICDD Poster Draws a Crowd; will be on long-term display
CQD ICDD Poster Draws a Crowd; will be on long-term display
Northwestern University McCormick News Article - March 16, 2011
The Center for Quantum Devices (CQD) team designed a poster for the 2011 International Centre for Diffraction Data (ICDD) Spring Meeting, held March 14-18, 2011 in Newton Square, PA. The poster, entitled "Ultraviolet Towards Terahertz III-Nitrode Optoelectronic Devices," was such a success that the ICDD president requested the poster be kept on display throughout the year. The team consists of PhD students Can Bayram, and Yinjun Zhang; Research Scientists Dr. Zahra Vashasi and Dr. Ryan McClintock; Collaborators Dr. Ferechteh Teherani, Dr. Dave Rogers, and Principal Investigator Prof. Manijeh Razeghi. ... [read more]
 
78.  
Researchers Create World’s First High Performance Infrared Camera Based on Type-II InAs/GaSb Superlattices
Researchers Create World’s First High Performance Infrared Camera Based on Type-II InAs/GaSb Superlattices
Northwestern University McCormick News Article - November 15, 2010
Researchers from the Center for Quantum Devices at Northwestern University have created a new large-format infrared camera based on Type-II InAs/GaSb superlattices that produces much higher resolution images than previous infrared cameras. Created by Manijeh Razeghi and her group, the long wavelength infrared focal plane array camera provides a 16-fold increase in the number of pixels in the image. Their results were recently published in the journal Applied Physics Letters, Volume 97, Issue 19, 193505 (2010). The goal of the research is to offer a better alternative to existing long wavelength infrared radiation (LWIR) cameras, which, with their thermal imaging capabilities, are used in everything from electrical inspections to security and nighttime surveillance. Current LWIR cameras are based on mercury cadmium telluride (MCT) materials, but the Type-II superlattice is mercury-free, more robust, and can be deposited with better uniformity. This will significantly increase yield and reduce camera cost once the technology goes commercial. ... [read more]
 
79.  
Researchers Create High-Power Single Mode Quantum Cascade Lasers
Researchers Create High-Power Single Mode Quantum Cascade Lasers
Northwestern University McCormick News Article - November 8, 2010
New laser technology developed by researchers at the Center for Quantum Devices may soon allow long-distance chemical analysis that could potentially be used in spills and warfare. Because chemicals absorb light in the infrared, it is possible to detect specific chemicals by using a laser and analyzing the returned light. But this long-distance mapping of chemicals by laser isn’t yet possible because researchers haven’t created a suitable laser source. Manijeh Razeghi and her group have created new laser technology that combines the high-power output of a broad area mid-infrared quantum cascade laser (QCL) with a two-dimensional diffractive resonator design that controls both the wavelength and beam quality with the laser. This led to the demonstration of up to 34 watts of peak power at room temperature and near-diffraction-limited beam quality at 4.3 μm, which is near the absorption frequency of several important chemicals. That represents almost a significant improvement in output power for this type of laser source. ... [read more]
 
80.  
European Semiconductor Laser Workshop at Pavia University in Italy
European Semiconductor Laser Workshop at Pavia University in Italy
La Provencia - September 22, 2010
Among the invited speakers, in particular, there will be Manijeh Razeghi, one of the first scientists to develop semiconductor lasers in Europe in the '80s ... [read more]
 

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