Terahertz Bessel metalens with an extended non-diffractive length and a high efficiency

Area of Science:

• Optics and Photonics
• Metamaterials
• Terahertz (THz) Technology

Background:

• Bessel beams offer unique non-diffractive properties crucial for advanced imaging.
• Existing Bessel beam generators often face limitations in efficiency, size, or beam quality.
• Terahertz technology demands compact and efficient beam-shaping components.

Purpose of the Study:

• To propose and demonstrate a novel reflective terahertz Bessel metalens.
• To achieve high efficiency and a long non-diffractive length for Bessel beams.
• To utilize polarization-insensitive sub-wavelength structures for robust performance.

Main Methods:

• Design of a reflective metalens incorporating hyperboloidal and conical phase profiles.
• Utilizing sub-wavelength metal resonator-dielectric-metal structures for polarization insensitivity.
• Experimental characterization of focusing efficiency and non-diffractive length.

Main Results:

• Demonstrated a reflective terahertz Bessel metalens with a focusing efficiency of 72.1%.
• Achieved a significant non-diffractive length of 239 wavelengths (239λ).
• The metalens operates effectively due to its polarization-insensitive design.

Conclusions:

• The proposed Bessel metalens offers a high-performance solution for generating non-diffractive beams in the terahertz spectrum.
• The device exhibits promising potential for miniaturized and integrated terahertz imaging systems.
• The polarization-insensitive design enhances the practical applicability of the Bessel metalens.