Thickness bound for nonlocal wide-field-of-view metalenses

Area of Science:

• * Optics and Photonics
• * Metasurface Technology
• * Imaging Systems

Background:

• * Metalenses, flat lenses utilizing optical metasurfaces, offer potential for compact, cost-effective imaging systems.
• * A wide angular field of view (FOV) is critical for metalens applications but necessitates angle-dependent optical responses.
• * Current metalens designs face challenges in balancing FOV with device miniaturization.

Purpose of the Study:

• * To investigate the fundamental trade-off between metalens thickness and achieving a broad angular response.
• * To establish a theoretical framework for predicting the minimum achievable thickness for a desired FOV.
• * To provide design guidelines for nonlocal metasurfaces with tailored angular characteristics.

Main Methods:

• * Utilized Fourier transform duality between spatial and angular domains to analyze device nonlocality.
• * Developed a method to quantify the required lateral spreading based on the transmission matrix.
• * Derived a formula for the minimal device thickness as a function of FOV, lens diameter, and numerical aperture.

Main Results:

• * Demonstrated an intrinsic trade-off limiting the simultaneous optimization of metalens thickness and broad-angle performance.
• * Quantified this limitation by establishing a thickness bound derived from the spatial-angular duality.
• * Showed that advanced inverse-designed multi-layer metasurfaces can approach these theoretical thickness limits.

Conclusions:

• * The study provides a general framework for establishing bounds on the performance of nonlocal metasurfaces.
• * Offers critical insights into the relationship between angular diversity and spatial footprint in optical systems.
• * Guides the design of next-generation metalenses with enhanced wide-field imaging capabilities.