Subwavelength-thick Lenses with High Numerical Apertures and Large Efficiency Based on High Contrast Transmitarrays

TL;DR

This paper introduces ultra-thin, high-efficiency micro-lenses operating at telecom wavelengths, utilizing high contrast transmitarrays to achieve small focal spots and high numerical apertures suitable for scalable manufacturing.

Contribution

The work presents a novel design of subwavelength-thick, polarization-insensitive micro-lenses based on high contrast transmitarrays, with a rigorous design method and practical fabrication approach.

Findings

Focal spots as small as 0.57 wavelengths

Focusing efficiency up to 82%

Potential for scalable manufacturing

Abstract

We report subwavelength-thick, polarization insensitive micro-lenses operating at telecom wavelength with focal spots as small as 0.57 wavelengths and measured focusing efficiency up to 82%. The lens design is based on high contrast transmitarrays that enable control of optical phase fronts with subwavelength spatial resolution. A rigorous method for ultra-thin lens design, and the trade-off between high efficiency and small spot size (or large numerical aperture) are discussed. The transmitarrays, composed of silicon nano-posts on glass, could be fabricated by high-throughput photo or nanoimprint lithography, thus enabling widespread adoption.