Terahertz Spectroscopy And Imaging Based On A Soft Lock-in Implementation

Recent development of terahertz time-domain spectrometers associated with a scanning imaging module gave rise to higher levels of detection and identification performances by hyperspectral imaging in the terahertz range. In this work, we present the latest results of our implemented terahertz imaging system based on a terahertz time-domain spectrometer setup associated with a raster scanning module. The image is created pixel by pixel by moving the object in X and Y directions in the focal plane of the terahertz beam using two linear stages. The device can be used simultaneously to provide a terahertz intensity image of an object as well as to record the temporal forms of the transmitted terahertz pulses at each point of the object. The resulting image describes the object transmittance in terahertz domain while the temporal forms may be used to perform other advanced signal processing. The terahertz beam is generated and detected using two photoconductive antennas is very weak, to face this challenge and improve detection efficiency, the use of a lock-in system is necessary especially when the materials under test are very absorbent. Thus, a soft lock-in detection method is implemented to reduce the noise of the electro-optic detection and thus increase the detection efficiency.