The unique characteristics of THz radiation make it useful in such applications as medical imaging (for example cancer detection), materials characterization, high speed communications, and homeland security surveillance.
The way it gets selectively transmitted or absorbed by different materials enables imaging through optically opaque materials in security applications. Terahertz wavelength radiation may also be used to analyze the inner structure of materials, medicine, or food due to the unique spectral signature of various compounds in the THz spectral region. This has opened many possibilities for spectroscopic analysis in industrial and scientific applications.
As in any application involving precise use of light, measurement becomes an important issue. Measurement of THz radiation, though - especially calibrated measurement -presents some technical challenges:
- Power levels are as low as nW, up to several hundred mW.
- The low photon energy (in the range of meV) makes detection using photodiode sensors very difficult. This means that thermal or pyro-electric sensors are needed – but they are normally not quite sensitive enough.
- Finding a suitable absorber for the THz spectral region is not trivial.