Experimental characterization of terajet generated from dielectric cuboid under different illumination conditions

The terajet, which is the generation of a jet in the terahertz (THz) frequency band (0.1 THz-10 THz), has attracted significant research interest owing to its subwavelength hotspot that can be exploited in THz imaging applications. To date, the generation of the terajet from a dielectric cuboid has been studied and verified under planar incidences. In practical applications of high-resolution THz imaging, it is essential to take into consideration the alignment of the cuboid, as well as the efficient use of the THz power. Here, we experimentally study the generation of the terajet under different oblique and compressed incidences, in order to verify the characteristics of the terajet, such as the position, direction, and full width at half maximum (FWHM) properties. We discover that the terajet can be generated under compressed incidence. The output angle of the terajet under oblique incidence is linear and identical to the input angle of the incident beam. The position of the generated terajet is varied within two wavelengths. The FWHW below one wavelength was maintained under those illumination conditions. Consequently, the cuboid can function as a novel focusing device, which can enhance the resolution by simply placing it in the imaging system with a flexible alignment.