“On-the-Fly” Monitoring With a Single-Shot Terahertz Time-Domain Spectrometer

We demonstrate the application of a new and ultrafast terahertz (THz) time-domain spectrometer for the nondestructive evaluation of targets that are optically opaque and are composed of several subunits. Thanks to the single-shot capability and the kilohertz acquisition rate of the spectrometer, objects can be analyzed during free fall. The integrity of the objects and their structural subunits as packaging material can be verified by the large amount of information available from THz time-domain spectroscopy. The time of flight, overall absorption, and spectrally resolved absorption can be used to reconstruct the 2-D image along the vertical axis of movement and the depth of the objects.