New weapon against terror

Researchers at Northwestern University's Center for Quantum Devices have demonstrated a specialised diode laser that holds promise as a weapon of defence in both civilian and military applications. Once optimised, the tiny laser could quickly detect explosives and chemical warfare agents (CWAs) early and warn against possible threats.

The Northwestern team, led by centre director Manijeh Razeghi, became the first to create a quantum cascade laser (QCL) that can operate continuously at high power and at room temperature with an emission wavelength of 9.5 microns and a light output of greater than 100 milliwatts.

Existing standard diode lasers, such as those used to read compact discs or barcodes, do not operate effectively in the longer wavelengths that are required to detect CWAs. The challenge for researchers around the world has been to develop a portable laser that operates in the far-infrared (wavelengths of 8 to 12 microns). Every chemical has a unique "fingerprint" because it absorbs light of a specific frequency, and most CWAs fall in the 8 to 12 micron region.