Terahertz super-resolution imaging with large depth of field enabled by the terajet of bilayer dielectric spheres.

Terahertz imaging has found extensive applications in non-destructive testing, security inspection, and other various fields. Intensive research on terahertz imaging systems has been executed to pursue high performance on imaging resolution and depth of field (DOF). However, the terahertz imaging systems with both high imaging resolution and large DOF have rarely been reported. In this paper, a mesoscopic-sized dielectric bilayer sphere-assisted super-resolution imaging method was proposed to simultaneously achieve enormously improved imaging resolution and extended DOF. Simulation analyses revealed that the ultrathin and long terajets were generated by the well-designed bilayer sphere. The THz super-resolution image for the samples can be captured by the point-by-point terajet scanning. The experimental results demonstrated that the best resolution reached up to 0.4λ, the DOF with super-resolution was up to 2λ, and the DOF with sub-wavelength resolution was up to 4λ. This method holds great potential for widespread application in terahertz imaging and detection, especially for curved or complex sample structures.