Several types of lasers exist today that can emit at desired infrared wavelengths, none of these lasers meet requirements for some applications because they are either too expensive, not mass-producible, too fragile or require power-hungry and inefficient cryogenic refrigeration. Applications for suitably portable laser systems include 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.
A new type of semiconductor-based laser, called the Quantum Cascade Laser (QCL) are compact and suitable for mass production and 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.
Demonstrations have been made of individual QCL 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. The lasers are 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.