Tightly focusing metalens based on the high order Bessel function.

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Metalenses offer miniaturized optical components with advanced functionalities.
• Traditional metalenses often face limitations in generating complex light field distributions.

Purpose of the Study:

• To introduce a new type of metalens based on higher-order Bessel functions.
• To demonstrate a method for designing geometric-phase dielectric metasurfaces for phase and polarization control.
• To achieve tightly focused light beams with circular trajectories.

Main Methods:

• Phase profile extraction from higher-order Bessel functions.
• Phase binarization technique for metasurface design.
• Fabrication and characterization of dielectric metasurfaces.
• Demonstration with circularly and radially polarized output beams at 633 nm.

Main Results:

• Achieved measured focal spots of 0.737λ and 0.616λ for different polarization outputs.
• Demonstrated the capability to generate tightly focusing fields along circular trajectories.
• Theoretically predicted super-diffraction-limit focusing down to 0.38λ.

Conclusions:

• The proposed metalens design represents a novel approach for creating advanced optical devices.
• This work extends the possibilities for realizing tightly focused optical systems with complex beam shaping.
• The developed metasurface design allows for simultaneous phase and polarization modulation.