Terahertz Polarization Imaging and Its Applications

Abstract

This review focuses on several recent research activities regarding precise and fast polarization-sensitive terahertz time-domain spectroscopy systems for imaging purposes, and explains three interesting application examples. Owing to modulation techniques that have recently been developed for the evaluation of the instantaneous terahertz electric-field (E-field) vector, fast and precise terahertz polarization imaging becomes feasible. This terahertz technology enables high-resolution surface topography, precise understanding of the spatial E-field vector distribution of the focused terahertz pulse, and examination of strain-induced birefringence in polymeric materials. These examples constitute a new application area of terahertz photonics with emphasis on both fundamental optics and industrial applications.

Optical Reconfigurable Terahertz Devices using Phase Change Materials

“…The strong contrast in THz amplitude signals transmitted through the GeTe films optically prepared in the two different states suggests that simple structures made only in GeTe (without additional metallic structures) could be feasible, offering interesting and promising opportunities for developing active THz reconfigurable devices. In particular, THz polarizers are essential devices, with critical roles in imaging and wireless communication applications [46][47][48][49] . For demonstrating the potential capabilities of the GeTe material for these applications,…”

Review on polarimetric terahertz spectroscopy

“…In the past 30 years from its emerging, THz‐TDS has attracted lots of attentions and has wide applications on biomedicine and NDI, at present, THz‐TDS is the main method of spectroscopy in the THz band. In principle, THz‐TDS is a measurement method in time domain, and its frequency‐domain information is further calculated out by using fast Fourier transform (FFT), but this is based on an assumption, the THz wave passing through sample still satisfies coherence, and this condition may not meet sometimes 6 . In contrast to THz‐TDS, THz‐FDS is a measurement method in frequency domain and it scan the spectrum directly with a narrow linewidth THz laser.…”

“…The overall polarization effect is that the system is like a polarization filter at some wavelengths, the amplitude at these wavelengths will be reduced, and thus conventional THz‐TDS and conventional THz‐FDS will misinterpret the minima as a normal spectral absorption wavelength, finally this leads to wrong conclusions on the samples. Therefore, in order to detect unknown materials, THz system must have polarization auto‐test function, we must investigate comprehensively polarimetric THz‐TDS and polarimetric THz‐TDS, this has become very hot topic in global THz research 6‐10 . Polarimetric THz‐TDS and polarimetric THz‐FDS are brand‐new technologies which were upgraded from conventional THz‐FDS and conventional THz‐FDS, respectively.…”

Active meta polarizer for terahertz frequencies

“…Terahertz radiations, with their extraordinary advantages (large bandwidth, traveling in a line of sight, good penetration and non-ionizing) offer unprecedented capabilities in applications spanning from medical imaging 1 , security 2 , radar 3 , high-speed communications 4 to spectroscopy of complex molecular networks 5 . In particular, active polarizers play an important role in terahertz imaging and wireless communication systems, which are essential for improving imaging and communication qualities 6 , 7 . Recent technologies of adaptive control of propagating terahertz wave polarizations are based on meta-devices (collection of coupled identical meta-atoms) which modify their intrinsic overall topology through mechanical, optical, electrical and thermal stimuli 8 – 33 .…”