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41.  
New Infrared Photodetectors Improve Medical Screening
New Infrared Photodetectors Improve Medical Screening
McCormick Press Release - January 29, 2015
Led by Professor Manijeh Razeghi, members of Northwestern University’s Center for Quantum Devices have improved the stability and lowered the cost of mid- and long-wavelength infrared photodetectors and focal plane array cameras. They achieved this by, first, using a novel type-II superlattice material called gallium-free indium-arsenide/indium-arsenide-antimonide or mercury-cadmium-telluride material. This design can be tuned to absorb a wide range of infrared wavelengths and a number of distinct infrared bands at the same time. This work is described in a paper published in the January 8 issue of Applied Physics Letters, the research was partially funded by DARPA, the Army Research Laboratory, the Air Force Research Laboratory, and NASA. ... [read more]
 
42.  
Infrared Imaging Technique Operates at High Temperatures
Infrared Imaging Technique Operates at High Temperatures
McCormick Press Release - January 23, 2015
From aerial surveillance to cancer detection, mid-wavelength infrared (MWIR) radiation has a wide range of applications. And as the uses for high-sensitivity, high-resolution imaging continue to expand, MWIR sources are becoming more attractive. A team of researchers at Northwestern University’s Center for Quantum Devices (CQD) has incorporated new materials to develop detectors that can work at room temperature. Razeghi and her group developed an indium arsenide/gallium antimonide (InAs/GaSb) type II superlattice that demonstrated high-resolution MWIR images while operating at high temperatures. The new technique was particularly successful at obtaining infrared images of the human body, which has potential for vascular imaging and disease detection. ... [read more]
 
43.  
Terahertz radiation from mid-infrared quantum cascade lasers
Terahertz radiation from mid-infrared quantum cascade lasers
Semiconductor Today - December 11, 2014
Northwestern University’s Center for Quantum Devices in USA has developed a monolithic room-temperature terahertz (THz) source based on quantum cascade lasers (QCLs) [Q. Y. Lu et al, Appl. Phys. Lett., vol105, p201102, 2014]. The resulting device is tunable over the range 2.6THz-4.2THz, i.e. 47% of the central frequency. The team claims that the device is the first room-temperature, multi-section, two-color SGDFB-DBR structure to realize a monolithic tunable THz source.The researchers believe: “Higher THz power and continuous-wave operation can be further obtained by using a device structure with a higher THz conversion efficiency and better thermal packaging.” (Link) ... [read more]
 
44.  
New Terahertz Device Could Strengthen Security
New Terahertz Device Could Strengthen Security
McCormick Press Release - November 20, 2014
current terahertz sources are large, multi-component systems that sometimes require complex vacuum systems, external pump lasers, and even cryogenic cooling. The unwieldy devices are heavy, expensive, and hard to transport, operate, and maintain. A single-component solution capable of room temperature and widely tunable operation is highly desirable to enable next generation terahertz systems. In a recent paper in Applied Physics Letters, they demonstrate a room temperature, highly tunable, high power terahertz source. Based on nonlinear mixing in quantum cascade lasers, the source can emit up to 1.9 milliwatts of power and has a wide frequency coverage of 1 to 4.6 terahertz. By designing a multi-section, sampled-grating distribution feedback and distributed Bragg reflector waveguide, Razeghi and her team were also able to give the device a tuning range of 2.6 to 4.2 terahertz at room temperature. ... [read more]
 
45.  
View from... IQCLSW 2014: Frequency comb cascade
View from... IQCLSW 2014: Frequency comb cascade
NATURE PHOTONICS | NEWS AND VIEWS - October 31, 2014
This year marks the 20th anniversary of the first experimental demonstration of QCL, but rather than looking back on the history of QCLs the workshop was focused on leading-edge research. It featured about 150 presentations, including both oral and poster, and attracted more than 200 researchers from 15 countries. An emerging topic of discussion at the conference was ultrabroadband tunable QCLs. Manijeh Razeghi of Northwestern University, USA, reported broadband tuning over 5.7–9.3 μm using a heterogeneous structure. She is now trying to extend the tunability even further. “Imagine having a QCL source that is electrically tunable across the entire mid-infrared range of 3–12 μm,” she said. “This would revolutionize mid-infrared spectroscopy and perhaps enable new applications as well.” ... [read more]
 
46.  
New Technology Illuminates Colder Objects in Deep Space
New Technology Illuminates Colder Objects in Deep Space
McCormick Press Release - July 8, 2014
“High performance infrared cameras are crucial for space exploration missions,” said Manijeh Razeghi, the Walter P. Murphy Professor of Electrical Engineering and Computer Science in the McCormick School of Engineering and Applied Science. “By studying the infrared waves emitted by cool stars and planets, scientists are beginning to unlock the mysteries of these cooler objects.” Published in the June 23 issue of Applied Physics Letters, Razeghi and her collaborators describe a new technology, which uses a novel type II superlattice material called indium arsenide/indium arsenide antimonide (InAs/InAsSb). The technology shows a stable optical response in regards to very long wavelength infrared light. By engineering the quantum properties of the type II superlattice material, the team demonstrated the world’s first InAs/InAsSb very long wavelength infrared photodiodes with high performance. The new detector can be used as an inexpensive and robust alternative to current infrared technologies. ... [read more]
 
47.  
 Team Demonstrates Continuous Terahertz Sources at Room Temperature
Team Demonstrates Continuous Terahertz Sources at Room Temperature
McCormick Press Release - June 4, 2014
Imagine a technology that could allow us to see through opaque surfaces without exposure to harmful x-rays, that could give us the ability to detect harmful chemicals and bio-agents from a safe distance, and that could enable us to peer so deeply into space that scientists could better understand the formation of the universe. All of these scenarios are possible with terahertz radiation, electromagnetic waves with lengths that fall between microwaves and infrared light. However, the potential of terahertz waves has yet to be reached because they are difficult to generate and manipulate. Current terahertz sources are large, multi-component systems that require complex vacuum electronics, external pump lasers, or cryogenic cooling. It’s an expensive and cumbersome process. Manijeh Razeghi and her team are the first to produce terahertz radiation in a simplified system, making it easier to harness the power of these elusive waves. They have developed the first room-temperature, compact, continuous terahertz radiation source, and it’s six times more efficient than previous systems. ... [read more]
 
48.  
Accelerating adoption of GaN substrates for LED manufacture
Accelerating adoption of GaN substrates for LED manufacture
Compound Semiconductor Magazine - June 1, 2014
COMMERCIALISATION of the GaN LED can be traced back to the development of p-type doping of this wide bandgap semiconductor in the early 1990s. Since then, the performance of this device has improved exponentially, enabling it to progress from use in the backlighting of mobile screens to providing a source for solid-state lighting. However, although LED lighting is now commonplace, its cost-performance profi le has a long way to go untill the incumbent vacuum-tubebased lighting technologies will cease to dominate. One of today’s key bottlenecks is the requirement to use a ‘non-native’ substrate. A new substrate option that has attracted a signifi cant amount of attention is ZnO, which not only has the same crystal structure as GaN, but also very similar lattice parameters and comparable thermal expansion coefficients. ... [read more]
 
49.  
Razeghi Authors Technical Article in International Society for Optics and Photonics (SPIE)
Razeghi Authors Technical Article in International Society for Optics and Photonics (SPIE)
EECS Newsroom - January 10, 2014
Razeghi1-oct3 2Manijeh Razeghi, Walter P. Murphy Professor, Director, Center for Quantum Devices (CQD) wrote a featured technical article, titled, "Quantum Cascade Lasers for IR and THz Spectroscopy," that was published December 16, 2013, on the International Society for Optics and Photonics (SPIE) website for her recent research on demonstrating increased power, spectral coverage, and tunability of quantum cascade lasers. Prof. Razeghi's recent publication, focuses on how developing quantum cascade lasers (QCLs) with the highest power, efficiency, and tunability. Unlike traditional diode lasers, the QCL has a series of quantum wells, which split the usual electron bands into subbands. The QCL emits over several intersubband transitions in this structure. Her CQD team can engineer its optical response using quantum size effects, to achieve a highly variable emitting wavelength based on nanometer-scale control of the quantum well thickness. They demonstrated room-temperature QCLs covering both the 3–16μm and 65–300μm wavelength ranges using an indium phosphide (InP) material system. ... [read more]
 
50.  
Quantum cascade lasers for IR and THz spectroscopy
Quantum cascade lasers for IR and THz spectroscopy
SPIE Newsroom - December 22, 2013
Terahertz spectroscopy is widely used for chemical detection, and has applications in quality control for manufacturing, security screening, and astronomy. Most chemicals absorb in the mid-IR and THz spectral regions, which cover a wavelength range of 3–300 microns. During our research1 we developed quantum cascade lasers (QCLs) with the highest power, efficiency, and tunability. Unlike traditional diode lasers, the QCL has a series of quantum wells, which split the usual electron bands into subbands. The QCL emits over several intersubband transitions in this structure. We can engineer its optical response using quantum size effects, to achieve a highly variable emitting wavelength based on nanometer-scale control of the quantum well thickness. We demonstrated room-temperature QCLs covering both the 3–16μm and 65–300μm wavelength ranges. ... [read more]
 

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