Phase-controlled metasurface design via optimized genetic algorithm

Nanophotonics

article

Yulong Fan¹  Yunkun Xu¹  Meng Qiu²  Wei Jin²  Lei Zhang³  Edmund Y. Lam⁴  Din Ping Tsai⁵  Dangyuan Lei¹ 

[1] City University of Hong Kong, Department of Materials Science and Engineering;The Hong Kong Polytechnic University, Department of Electrical Engineering;The Hong Kong Polytechnic University, Department of Computing;The University of Hong Kong, Department of Electrical and Electronic Engineering;The Hong Kong Polytechnic University, Department of Electronic and Information Engineering

关键词: dielectric metasurface;    genetic algorithm;    light sheet;    optical Pancharatnam-Berry phase;   

DOI  :  10.1515/nanoph-2020-0132

学科分类：社会科学、人文和艺术（综合）

来源: De Gruyter

【 摘 要 】

In an optical Pancharatnam-Berry (PB) phase metasurface, each sub-wavelength dielectric structure of varied spatial orientation can be treated as a point source with the same amplitude yet varied relative phase. In this work, we introduce an optimized genetic algorithm (GA) method for the synthesis of one-dimensional (1D) PB phase-controlled dielectric metasurfaces by seeking for optimized phase profile solutions, which differs from previously reported amplitude-controlled GA method only applicable to generate transverse optical modes with plasmonic metasurfaces. The GA–optimized phase profiles can be readily used to construct dielectric metasurfaces with improved functionalities. The loop of phase-controlled GA consists of initialization, random mutation, screened evolution, and duplication. Here random mutation is realized by changing the phase of each unit cell, and this process should be efficient to obtain enough mutations to drive the whole GA process under supervision of appropriate mutation boundary. A well-chosen fitness function ensures the right direction of screened evolution, and the duplication process guarantees an equilibrated number of generated light patterns. Importantly, we optimize the GA loop by introducing a multi-step hierarchical mutation process to break local optimum limits. We demonstrate the validity of our optimized GA method by generating longitudinal optical modes (i. e., non-diffractive light sheets) with 1D PB phase dielectric metasurfaces having non-analytical counter-intuitive phase profiles. The produced large-area, long-distance light sheets could be used for realizing high-speed, low-noise light-sheet microscopy. Additionally, a simplified 3D light pattern generated by a 2D PB phase metasurface further reveals the potential of our optimized GA method for manipulating truly 3D light fields.

【 授权许可】

CC BY