Terahertz frequencies 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.
This is 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.
The new camera is based on technology that is said to have the potential to lower production costs and enable future mass production of terahertz cameras and imagers. 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, which 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 to 3.0THz) 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 to 1.5THz) is expected to expand the fields of application, and uses a completely new type of terahertz sensor that enables operation at room temperature. Normally, terahertz sensors require expensive cryogenic cooling to temperatures below -200°C to perform well.
The blend of advanced technologies for this camera led to improvements in thermal sensitivity and high-level integration of terahertz components. A demonstrator, comprising a 24 x 24 focal-plane-array of detectors and readout circuitry operating in video imaging mode, has been built and 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.
