A breakthrough in terahertz imaging: The on-chip terahertz camera developed by the TeraTOP consortium. © TeraTOP
Airbus Group Innovations, together with seven research partners, has made an important breakthrough in terahertz imaging technology which offers strong potential in the areas of space observation, medical imaging, industrial automation and security screening. Under the auspices of a European Union project called TeraTOP, consortium partners developed a new camera that delivers high accuracy using terahertz waves and promises lower production and operating costs.
Terahertz frequencies – which correspond to 300 gigahertz to 10 terahertz – occupy a section of the electromagnetic spectrum between the microwave and the optical. When used for security screening applications, for example, terahertz imagers provide higher-resolution images than existing millimetre wave imagers. But while the use of other parts of the electromagnetic spectrum – from X-rays to millimetre waves – is ubiquitous in today’s imaging technology, the terahertz frequency remains mostly underutilised despite decades of research. That’s because existing applications tend to have complex manufacturing processes and require extensive cooling during operation – resulting in prohibitively high production and operating costs and correspondingly low market demand.
TeraTOP was launched in 2011 and successfully tackled both technological and cost issues over the course of the 45-month project: The new camera is based on technology that has the potential to significantly lower production costs and enable future mass production of terahertz cameras and imagers – a big step forward in advancing the commercial use of terahertz technology for imaging in the future. Key to TeraTOP’s research was determining an appropriate strategy for developing and producing a terahertz imaging device with complementary metal oxide semiconductor (CMOS) technology. As CMOS technology is widely used today in computer processors and mobile phone camera chips, it promises the reduction of production costs as well as improvements in performance.
Recent developments in the field of electronic imaging based on CMOS technology have generated enormous business opportunities worldwide. Today’s imaging technologies almost solely detect the visible and near-infrared part of the electromagnetic spectrum. So far, the development of analogous capabilities in the terahertz range (0.3 THz - 3.0 THz) has focused primarily on exotic materials and has been impeded by the lack of devices and circuits suitable for mass production. The new chip-integrated camera (0.5 -1.5 THz) is expected to expand the fields of application, and uses a completely new type of terahertz sensor that enables operation at room temperature. This gives it a clear advantage over terahertz sensors that normally require expensive cryogenic cooling to temperatures below minus 200°C to perform well.
The blend of advanced technologies for this new camera led to improvements in thermal sensitivity and high-level integration of terahertz components. A demonstrator, comprising a 24x24 focal-plane-array (FPA) of detectors and readout circuitry operating in video imaging mode, was built, and its full functionality successfully tested.
The current camera design is suited for active terahertz imaging. Further development of CMOS-based terahertz technologies is expected to enhance sensitivity and also enable passive imaging applications.