New system to instantly detect explosives

Scientists have developed a new system that can extract the spectroscopic "fingerprints" in just 100 microseconds and identify a wide range of materials including chemicals used in explosives.
Terahertz spectroscopy uses the band of electromagnetic radiation between microwaves and infrared light.
However, traditional terahertz spectroscopy requires a radiation source that is heavy and about the size of a large suitcase, and it takes 15 to 30 minutes to analyse a single sample, rendering it impractical for most applications.
Scientists including those from Massachusetts Institute of Technology (MIT) in the US developed a new terahertz spectroscopy system that uses a quantum cascade laser, a source of terahertz radiation that is the size of a computer chip.

The system can extract a material's spectroscopic signature in just 100 microseconds.
The device is so efficient because it emits terahertz radiation in what is known as a "frequency comb," meaning a range of frequencies that are perfectly evenly spaced, researchers said.

Different materials absorb different frequencies of terahertz radiation to different degrees, giving each of them a unique terahertz-absorption profile.
As a proof of concept, the researchers used their system to measure the spectral signature of not a chemical sample but an optical device called an etalon, made from a wafer of gallium arsenide, whose spectral properties could be calculated theoretically in advance, providing a clear standard of comparison.

The system's measurements were a very good fit for the etalon's terahertz-transmission profile, suggesting that it could be useful for detecting chemicals.
The study was published in the journal Optica.