Symmetric accelerating beam generation via all-dielectric metasurfaces.

Hammad Ahmed,Arbab Abdur Rahim,Husnul Maab,Muhammad Mahmood Ali

doi:10.1039/d0ra04584e

Abstract

Traditionally, symmetric accelerating beam (SAB) generation requires bulky optical components, which hinder the miniaturization of optical systems. Recently, metasurfaces, which are composed of sub-wavelength features, have provided a captivating boulevard for the realization of ultra-thin and flat optical devices. Therefore, for the first time, we design and simulate all-dielectric metasurfaces based on an optical caustic approach to generate highly efficient SABs by tailoring the phase of an incident wave. The designed metasurface utilizes spatial distribution of optimized Nb2O5 nano-rods on SiO2 substrate to perform the phase modulation. In contrast with conventional accelerating beams, the generated SABs can follow any predefined propagation trajectory with unique features, such as symmetric intensity profile, autofocusing, and thin needle-like structure in their intensity profile. In addition to this, these beams have also shown the ability to avoid obstacles, placed in the direction of propagation of main lobes. We believe that these beams can be useful in applications, including Raman spectroscopy and fluorescent imaging, and multiparticle manipulation.

Highlights

Over the past few years, accelerating beams have attracted the attention of researchers owing to their unprecedented properties, i.e., non-diffraction, self-acceleration, and self-healing
The larger pixel size of spatial light modulator (SLM) affects the performance of optical systems.[5]
Inspired from the previous work, we propose singlelayered, ultra-thin, all-dielectric metasurfaces for symmetric accelerating beam (SAB) generation

Summary

Introduction

Over the past few years, accelerating beams have attracted the attention of researchers owing to their unprecedented properties, i.e., non-diffraction, self-acceleration, and self-healing. Inspired from the previous work, we propose singlelayered, ultra-thin, all-dielectric metasurfaces for symmetric accelerating beam (SAB) generation. This idea was rst theoretically presented in ref. The derived phase pro les are spatially distributed on metasurface through niobium pentoxide (Nb2O5) nano-rods. To other state-of-the-art materials such as titanium oxide (TiO2), silicon nitride (Si3N4), amorphous silicon hydrogenated (a-Si:H) and gallium nitride (GaN).[25,26] This unique property of low absorption is responsible for high transmission efficiency.[27] In this work, the phase manipulation of an incident linearly polarized light is performed by varying radii of well-optimized nano-rods while maintaining the high transmission efficiency. SABs contain a needlelike structure in its intensity pro le, which can be used in uorescent imaging and Raman spectroscopy.[29,30] we show the autofocusing characteristic of SABs, which can be used in laser ablation and nano-surgery.[24]

Design methodology

Conclusions