Phase characterisation of metalenses

Area of Science:

• Optics and Photonics
• Metamaterials
• Nanotechnology

Background:

• Metalenses offer superior performance and diverse applications but lack direct phase distribution measurement.
• Quantitative evaluation of metalens performance is hindered by the absence of direct phase measurement techniques.

Purpose of the Study:

• To develop and demonstrate an interferometric imaging system for direct phase distribution measurement of metalenses.
• To enable quantitative analysis of metalens performance, including chromatic aberration and focal length deviation.
• To facilitate metalens design optimization and defect detection for industrial applications.

Main Methods:

• Development of a single-shot interferometric imaging system.
• Measurement of the phase distribution of metalenses.
• Analysis of phase response to wavelength for different metalens types (Pancharatnam-Berry vs. propagation phase).
• Characterization of imaging performance using measured phase distribution.

Main Results:

• Direct measurement of metalens phase distribution is achieved with a single interferometric image.
• Negative chromatic aberration in monochromatic metalenses is analyzed.
• Wavelength-dependent phase response differences between Pancharatnam-Berry and propagation phase metalenses are observed.
• Focal length deviation from nominal values is identified for low numerical aperture metalenses, independent of fabrication errors.
• Quantitative characterization of metalens imaging performance is demonstrated.

Conclusions:

• The developed phase measurement system provides direct, quantitative insights into metalens performance.
• This technique aids designers in optimizing metalens designs and helps fabricators identify defects.
• The system is crucial for advancing metalens technology towards industrial applications.