Terahertz Reflection Imaging Research Articles

Reflection-type pulsed terahertz imaging with a phase-retrieval algorithm

We propose and demonstrate a scheme for two-dimensional terahertz reflection imaging using a time-domain phase-retrieval algorithm based on the dispersion relations of complex reflection coefficients. With this scheme, topographic images—as well as the dielectric functions of a structured sample—can be obtained. A composite sample made of a semiconductor and metals is characterized within depth and lateral errors of 50μm and 100μm.

Identification and classification of chemicals using terahertz reflective spectroscopic focal-plane imaging system

We present terahertz (THz) reflective spectroscopic focal-plane imaging of four explosive and bio-chemical materials (2, 4-DNT, Theophylline, RDX and Glutamic Acid) at a standoff imaging distance of 0.4 m. The 2 dimension (2-D) nature of this technique enables a fast acquisition time and is very close to a camera-like operation, compared to the most commonly used point emission-detection and raster scanning configuration. The samples are identified by their absorption peaks extracted from the negative derivative of the reflection coefficient respect to the frequency (-dr/dv) of each pixel. Classification of the samples is achieved by using minimum distance classifier and neural network methods with a rate of accuracy above 80% and a false alarm rate below 8%. This result supports the future application of THz time-domain spectroscopy (TDS) in standoff distance sensing, imaging, and identification.