New camera system taps into terahertz wavelengths for better imaging

A team of engineers has developed a new type of camera that can detect radiation in terahertz (THz) wavelengths. This new imaging system can see through certain materials in high detail, which could make it useful for security scanners and other sensors.

Terahertz radiation is that which has wavelengths between microwaves and visible light, and these frequencies show promise in a new class of imaging systems. They can penetrate many materials and capture new levels of detail, and importantly the radiation is non-ionizing, meaning it’s safer than X-rays when used on humans.

The problem is that detectors that pick up THz wavelengths can be bulky, slow, expensive, difficult to run under practical conditions, or some combination of these. But in a new study, researchers at MIT, Samsung and the University of Minnesota have developed a system that can detect THz pulses quickly, precisely and at regular room temperature and pressure.

The key to the new system is what are known as quantum dots. Recent work has shown that these tiny particles will fluoresce in visible light when they’re struck by terahertz waves, and that visible light can then be captured by a conventional camera detector. The resulting image can not only detect low-intensity THz pulses, but also potentially reveal the polarization of the beam.

The device is made up of multiple layers in a stack. The first is an array of nanoscale lines of gold separated by narrow slits, followed by a layer of the quantum dots. Above that sits a conventional CMOS image sensor, which picks up the visible light emitted by the quantum dots when they’re struck by the incoming terahertz waves. For the version of the detector that can capture the polarization of the beam, the horizontal slits are replaced by a layer of ring-shaped slits.

In tests, the team says that the new device was able to pick up THz pulses at intensity levels far lower than existing systems can, while also being much smaller and cheaper to make. In fact, each layer of the device can be manufactured using current techniques for fabricating microchips. The cherry on top is that no current systems can capture the polarization.

There is, however, still plenty of work to do before this tech might be ready for commercialization. In particular, the team says that sources of THz radiation are still quite cumbersome, but their complexity will also likely come down in future.

Imaging isn’t the only potential use for THz radiation on the horizon – these wavelengths are also poised to become the basis for 6G communications systems in the next decade or so.

The new study was published in the journal Nature Nanotechnology.

Source: MIT