Overview #

This project was carried out under the A*STAR Institute of High-Performance Computing (IHPC) and awarded Silver at the 25th Singapore Science and Engineering Fair.

You can take a look at the paper and the poster.

Abstract #

Metasurfaces are an emergent class of ultra-thin patterned optical films, enabling the manipulation of electromagnetic waves with unprecedented precision as compared to their counterparts in conventional optics. A critical problem in the study of metalenses involves its structural designing, a concern hindered by plethoric degrees of freedom that presents in various optimisation problems.

In this paper, we characterise inverse design and demonstrate the gradient-based optimisation of achromatic metalenses using the adjoint method, through the development of mathematical models pertaining to back-propagation of electromagnetic responses, penalisation filters and design field projection, and maximin optimisation with epigraph formulation.

Our designed metalenses are binary-constrained with single-layered gratings to guarantee concordance with lithographic fabrication requirements. We employ our optimisation workflow to investigate achromatic behaviour at numerical apertures 0.1 to 0.5, demonstrating high-performance capabilities at low and medium-NA levels. Novel investigations are furthered by considering oblique incident planewaves of 15º, designing wide field-of-view metalenses that simultaneously possess achromatic properties.

Our research aids in advancing state-of-the-art metalens design, by substantiating an computationally inexpensive method of designing achromatic and multi-angle metastructure lenses that are able to exhibit efficient focusing of light.