A wave of drug busts

Scottish researchers are developing a hand-held Terahertz device to identify illegal drugs concealed within clothing, plastics, and potentially inside the human body.

Researchers at the University of St Andrews will next year build and test a prototype, based on an improved method of generating THz waves, in collaboration with crime science and technology specialist Forensic Alliance.

The team hopes that the use of THz waves will allow them to produce a portable device capable of distinguishing between different drugs, by detecting variations in frequency absorption between one type of molecule and another.

Other drug-detection methods — sniffer dogs and swiping the person or container with a trace detection system — rely on finding traces of the drug outside its packaging, but THz waves can see through paper, wood, plastic, fabrics, ceramics, bone, and human and animal tissue.

The new device will be based on a method of producing THz waves called parametric generation, said Malcolm Dunn, professor of photonics at St Andrews University.

‘If you take a non-linear crystal and put light through it, you can split the light photon into two parts. We put the light through a crystal and split off the part corresponding to THz radiation. Because you can alter where this splitting of the photon occurs in the non-linear medium, you can make it tuneable THz radiation,’ he said.

Unlike alternative methods of generating THz waves, such as quantum cascade lasers and photoconductive switching using ultrashort pulse lasers, parametric generation can produce radiation that can be tuned between frequencies of around 0.5 to 10 THz.

This will allow the device to target particular spectral features, allowing different drugs to be ‘fingerprinted’ through their frequency absorption characteristics. The radiation source can also operate at room temperature, unlike quantum cascade lasers, which must be cooled to cryogenic temperatures.

The team will build the prototype at the university’s Photonics Innovation Centre and test it using simulated drugs supplied by Forensic Alliance. Later the technology will be tested on real drugs at the company’s Culham laboratory, to determine how well it can identify different substances. The project has funding from the EPSRC.

A spokeswoman for Forensic Alliance said preliminary results for the technology looked ‘incredibly promising’.