A broadband terahertz ultrathin multi-focus lens

Area of Science:

• Optics and Photonics
• Metamaterials
• Terahertz Technology

Background:

• Terahertz (THz) radiation offers unique properties for imaging and sensing.
• Conventional THz focusing optics are often bulky and limited in functionality.
• Metasurfaces provide a novel platform for miniaturized and advanced optical devices.

Purpose of the Study:

• To design and demonstrate ultrathin transmission metasurface devices for generating multiple focal spots.
• To investigate the focusing performance and broadband characteristics of the designed THz multi-focus lens (TMFL).
• To evaluate the diffraction efficiency and imaging capabilities of the metasurface lens.

Main Methods:

• Utilized the Yang-Gu amplitude-phase retrieval algorithm for metasurface design.
• Fabricated ultrathin transmission metasurface devices.
• Experimentally characterized the focal properties, frequency response, diffraction efficiency, and imaging performance of the TMFL.

Main Results:

• Successfully focused terahertz radiation into four or nine spots with precise focal spacing.
• Achieved a broad operational frequency range from 0.3 to 1.1 THz.
• Demonstrated a high diffraction efficiency of up to 33.92% and obtained clear images.

Conclusions:

• The developed THz multi-focus lens is ultrathin, low-cost, and broadband.
• Metasurface-based devices offer a promising solution for advanced THz applications.
• The Yang-Gu algorithm is effective for designing complex metasurface functionalities.