Designing high-efficiency extended depth-of-focus metalens via topology-shape optimization

Area of Science:

• Optics and Photonics
• Metamaterials
• Computational Electromagnetics

Background:

• Longitudinal optical field modulation is crucial for advanced optical applications.
• Achieving a uniform light field with an extended depth-of-focus remains a significant challenge.
• Existing metalens designs often struggle with limited focal depth and efficiency.

Purpose of the Study:

• To propose and demonstrate a high-efficiency metalens with an extended depth-of-focus.
• To utilize an adjoint-based topology-shape optimization approach for metalens design.
• To enhance the theoretical electric field intensity and focal depth of metalenses.

Main Methods:

• Employed an adjoint-based topology-shape optimization method.
• Utilized theoretical electric field intensity corresponding to variable focal-length phase as the figure of merit.
• Initiated the optimization process with multiple metalenses possessing random structural parameters.

Main Results:

• Achieved a significantly improved average focal depth of 18.80 μm (approximately 29.7λ), 1.54 times greater than the diffraction-limited focal depth.
• Demonstrated high diffraction efficiency exceeding 0.7 across the entire focal depth range for optimized metalenses.
• The optimized metalenses showed approximately three times greater efficiency compared to forward design methods.

Conclusions:

• The adjoint-based topology-shape optimization approach is effective for designing extended depth-of-focus metalenses.
• The developed metalenses offer superior performance in terms of focal depth and diffraction efficiency.
• These findings provide new insights for designing advanced metalenses with potential applications in imaging, holography, and optical fabrication.