Applications of Broadband THz Bessel Beams Imaging Based on Transmission-Phase Metasurfaces

Transmission-phase metasurfaces are typically limited to the modulation of a single frequency, which restricts their application across broadband spectra. To enhance the depth of field in terahertz imaging systems and expand the use of metasurfaces in terahertz time-domain spectroscopy systems, a phase gradient was designed and a metasurface capable of generating Bessel beams was fabricated using a ceramic slurry. The results demonstrate that the metasurface can produce terahertz Bessel beams with a non-diffracting length of 160 mm approximately in the 0.4–0.6 THz frequency range while maintaining consistent non-diffracting regions across different frequencies. The imaging system exhibited stable lateral resolution and strong anti-interference capability, which effectively improved the depth of field in terahertz imaging. This study provides a novel method for generating broadband terahertz Bessel beams, extends the application of transmission-phase metasurfaces in terahertz time-domain spectroscopy systems, and has practical value for terahertz imaging and non-destructive testing.