Researchers at MIT and Princeton have built a new laser-powered terahertz spectroscopy system capable of detecting chemicals used in explosives.
Terahertz spectroscopy is the measurement of electromagnetic radiation between the frequencies of microwaves and infrared. Scientists have long realized the radiation’s potential for bomb detection, but traditional terahertz spectroscopy systems are bulky and use lots of power. They also take a long time to analyze sample materials.
The new system uses a computer chip-size quantum cascade laser, and can detect terahertz signatures in just 100 microseconds.
The device produces a laser-powered frequency comb — a spectrum made up of a series of equally spaced frequencies. The variety of frequencies allows the device to create a unique terahertz-absorption profile in just a few measurements.
The frequency comb is created by bouncing a laser back and forth through a gain medium composed of several hundred alternating layers of gallium arsenide and aluminum gallium arsenide. The layers are calibrated to propel the laser with just the right amount of energy to break through the gain medium.
Scientists tested their system by measuring the emissions frequency of an etalon, a double-mirrored wafer of gallium arsenide. Researchers were able to theoretically calculate the wafer’s transmission spectrum prior to their experiment.
Their calculations and the experimental results matched up neatly, proving their spectroscopy system reliable.
Read More: UPI
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