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Laser sets records in power and energy efficiency
July 24, 2007EVANSTON, Ill. --- The rise in global terrorism in recent years has brought significant attention to the needs for more advanced sensors and defense technologies to protect civilians and soldiers.
Next-generation laser-based defense systems are now being designed for this need, including the use of infrared countermeasures to protect aircraft from heat-seeking missiles and highly sensitive chemical detectors for reliable early detection of trace explosives and other toxins at a safe distance for personnel.
Since practical systems must be easily portable by a soldier, aircraft or unmanned vehicle, they must be lightweight, compact and power efficient. In addition, such systems also would need to be widely deployable and available to all soldiers, airplanes and public facilities, which requires a low production and operating cost. While several types of lasers exist today that can emit at the desired infrared wavelengths, none of these lasers meet the above requirements because they are either too expensive, not mass-producible, too fragile or require power-hungry and inefficient cryogenic refrigeration.
A new type of semiconductor-based laser, called the Quantum Cascade Laser (QCL), may soon change this situation. Like their computer chip cousins, semiconductors lasers are inherently compact and suitable for mass production, which has led to their widespread and low-cost use in everyday products, including CD and DVD players.
The Center for Quantum Devices (CQD) at Northwestern University, led by Manijeh Razeghi, Walter P. Murphy Professor of Electrical Engineering and Computer Science at the McCormick School of Engineering and Applied Science, has recently made great strides in laser design, material growth and laser fabrication that have greatly increased the output power and wall-plug efficiency (the ability to change electrical power into light) of QCLs.
The CQD now has demonstrated individual lasers, 300 of which can easily fit on a penny, emitting at wavelengths of 4.5 microns, capable of producing over 700 milli-Watts of continuous output power at room temperature and more than one Watt of output power at lower temperatures. Furthermore, these lasers are extremely efficient in converting electricity to light, having a 10 percent wall-plug efficiency at room temperature and more than 18 percent wall-plug efficiency at lower temperatures. This represents a factor of two increase in laser performance, which is far superior to any competing laser technology at this wavelength.
Northwestern University
A new type of semiconductor-based laser, called the Quantum Cascade Laser (QCL), may soon change this situation. Like their computer chip cousins, semiconductors lasers are inherently compact and suitable for mass production, which has led to their widespread and low-cost use in everyday products, including CD and DVD players.
The Center for Quantum Devices (CQD) at Northwestern University, led by Manijeh Razeghi, Walter P. Murphy Professor of Electrical Engineering and Computer Science at the McCormick School of Engineering and Applied Science, has recently made great strides in laser design, material growth and laser fabrication that have greatly increased the output power and wall-plug efficiency (the ability to change electrical power into light) of QCLs.
The CQD now has demonstrated individual lasers, 300 of which can easily fit on a penny, emitting at wavelengths of 4.5 microns, capable of producing over 700 milli-Watts of continuous output power at room temperature and more than one Watt of output power at lower temperatures. Furthermore, these lasers are extremely efficient in converting electricity to light, having a 10 percent wall-plug efficiency at room temperature and more than 18 percent wall-plug efficiency at lower temperatures. This represents a factor of two increase in laser performance, which is far superior to any competing laser technology at this wavelength.
Northwestern University
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Scientist proposes explanation for puzzling property of night-shining clouds at the edge of space
An explanation for a strange property of noctilucent clouds--thin, wispy clouds hovering at the edge of space at 85 km altitude--has been proposed by an experimental plasma physicist at the California Institute of Technology (Caltech), possibly laying to rest a decades-long mystery.
Bio-imaging mass spectrometry techniques reveal molecular details about complex systems
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UC Davis researchers find decrease in hysterectomy complications
UC Davis researchers who studied hospital discharge records for nearly 650,000 California women over a 13-year period have found that complications from hysterectomies have significantly declined.
Iowa State engineer works to clean and improve engine performance
The five engines in Song-Charng Kong's Iowa State University laboratory have come a long way since Karl Benz patented a two-stroke internal combustion engine in 1879.
Improving our ability to peek inside molecules
It's not easy to see a single molecule inside a living cell. Nevertheless, researchers at Lawrence Livermore National Laboratory are helping to develop a new technique that will enable them to create detailed high-resolution images, giving scientists an unprecedented look at the atomic structure of cellular molecules.
Colorful spy tactics track live cells supporting cancerous tumors
A new advance in cellular imaging is allowing scientists to better understand the movement of cells in the area around tumors, also known as the tumor microenvironment.
Researchers Discover Unexpected Properties of Materials in Lowermost Mantle
Materials deep inside Earth have unexpected atomic properties that might force earth scientists to revise their models of Earth's internal processes, a team of researchers has discovered.
Engineers develop a laser solution to power plants slowed by slagging
Quietly, and with little of the fanfare accompanying the relentless surge in gasoline costs, the price of coal has doubled in less than a year.
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