Terahertz metallic waveguide with meta-holes for focusing in the waveguide with unlimited focal length

The wave manipulation in the waveguide is of great importance for integrated terahertz (THz) signal processing and communication. Here, a design of metallic waveguide with meta-holes (MWMH) is proposed to realize focusing in the waveguide with unlimited focal length. When the MWMH is used to realize focusing with a focal-length of 45 mm, the gain at the focus can reach 26.8 dB and the focusing efficiency is 52.77% of the incident power. The full width at half maximum (FWHM) is 3 mm, and the depth of focus (DOF) is 22 mm. Furthermore, the MWMH for focusing with a focal-length of 10 mm and 0 mm are demonstrated, as illustrations of its flexible wave manipulation functions. The proposed MWMH with flexible wavefront manipulation functions opens up new possibilities for the development of THz integrated photonics devices, and has great potential in non-destructive testing, spectral imaging, and 6G wireless communication.