Broadband reflective terahertz metalens employing Bessel beams for enhanced efficiency and depth of focus.

This paper presents a reflective terahertz (THz) Bessel metalens with broadband operation in the frequency range of 0.80-1 THz. The design employs a near-wavelength, polarization-insensitive resonator to achieve a wideband response. Optimized at 0.89 THz, the metalens integrates a hyperbolic phase configuration combined with a conical phase profile. By varying the cone angle, the metalens attains a focusing efficiency of up to 76% and an extended depth of focus of 21.7λ. Simulations demonstrate superior performance compared to conventional focusing metalenses. This design shows significant potential for applications in terahertz imaging, communications, and sensing technologies.