Stretchable Dual-Axis Terahertz Bifocal Metalens with Flexibly Polarization-Dependent Focal Position and Direction

Area of Science:

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

Background:

• Traditional lenses are bulky and have fixed focal properties.
• Metalenses, composed of subwavelength structures, offer ultrathin profiles and tunable functionalities.
• Controlling phase distribution in metasurfaces is key to metalens performance.

Purpose of the Study:

• To propose and investigate seven designs of double-layer THz bifocal metalenses.
• To explore flexible tuning mechanisms for focal length and direction.
• To demonstrate polarization multiplexing for achieving dual foci.

Main Methods:

• Design and simulation of double-layer metalenses utilizing subwavelength structures.
• Investigating electromagnetic responses based on phase-shifting elements.
• Analyzing the interplay between focal length, direction, and polarization states.

Main Results:

• Demonstrated metalenses with tunable focal length and direction, showing dependent and independent relationships.
• Achieved polarization multiplexing, yielding two distinct foci for x- and y-linear polarizations.
• Simulation results showed excellent agreement with theoretical predictions.

Conclusions:

• The proposed metalenses offer precise focal position modulation.
• These designs provide a new method for advanced optical control.
• Promising applications in wireless communication, imaging, and on-chip optical integration.