Post by Oliver Graydon
The electromagnetic spectrum spans a rich range of wavelengths – from short-wavelength, highly energetic x-rays at one end through to long-wavelength radiowaves at the other. While many regions of this spectrum have already been explored by mankind and put to good use there is one that is still largely underexploited – that of terahertz waves. Lying in the region between infrared light and microwaves, terahertz waves (photons with a frequency between ~300 GHz and 10 THz), fall into a gap between the worlds of photonics and electronics. However, in recent years scientists have been increasingly exploring how such terahertz waves can be exploited. Historically, difficulties in efficiently generating and manipulating terahertz waves served as a barrier for the area. However, several developments have changed the fortunes of the field.
The advent of the quantum cascade laser in the mid-1990s provided access to a solid-state laser technology that evolved to emit milliwatts of power of terahertz radiation from a convenient semiconductor device, albeit cooled. More recently, engineered structures called “metamaterials” have been designed that can switch and modulate terahertz waves.
As for applications, researchers have found that terahertz waves can be useful for security screening, in particular. For example, it’s known that terahertz waves can pass through thin layers of clothing and organic materials but are blocked by metals, such as a knife blade, and that certain explosives and pharmaceuticals have a clear absorption fingerprint. As a result, several companies have since commercialized the technology for security scanners for use at airports and elsewhere. Other potential applications include the use of terahertz waves instead of radiowaves as a high-frequency carrier wave for future mobile communications opening the door to ultra-high-bandwidth data connections. There are also efforts to use terahertz waves for biomedical applications such as skin cancer detection, however the strong water absorption of terahertz waves limits many biological applications.
One thing’s for sure: the region is evolving from being a once neglected gap in the electromagnetic spectrum to a highly active area of science that is rich in potential applications and opportunities.