Ultra-broadband Tunable Resonant Light Trapping in a Two-dimensional Randomly Microstructured Plasmonic-photonic Absorber

Zhengqi Liu,Haiyang Lu,Mingjie Wan,Zhenlin Wang,Peng Zhan,Long Liu,Wei Du

doi:10.1038/srep43803

Abstract

Recently, techniques involving random patterns have made it possible to control the light trapping of microstructures over broad spectral and angular ranges, which provides a powerful approach for photon management in energy efficiency technologies. Here, we demonstrate a simple method to create a wideband near-unity light absorber by introducing a dense and random pattern of metal-capped monodispersed dielectric microspheres onto an opaque metal film; the absorber works due to the excitation of multiple optical and plasmonic resonant modes. To further expand the absorption bandwidth, two different-sized metal-capped dielectric microspheres were integrated into a densely packed monolayer on a metal back-reflector. This proposed ultra-broadband plasmonic-photonic super absorber demonstrates desirable optical trapping in dielectric region and slight dispersion over a large incident angle range. Without any effort to strictly control the spatial arrangement of the resonant elements, our absorber, which is based on a simple self-assembly process, has the critical merits of high reproducibility and scalability and represents a viable strategy for efficient energy technologies.

Highlights

On the other hand, based on their strong light concentration and scattering properties, light-trapping layers employing metallic plasmonic microstructures have gained significant attention recently[1,2,13,14]
A thin photoactive film drilled with a random pattern of holes demonstrates greater wideband light-trapping than one without holes and greater light-trapping than a periodic holes array; this might provide a powerful approach for photon management in energy efficiency technology, which could benefit from a lower amount of materials used and the possibility of better photoelectron conversion[35]
By optimizing the structural parameters of the absorber, such as the mixture ratio of these two different-sized microspheres and the thickness of the metallic cap over the PS beads, an ultra-broadband infrared absorption arising from effective modes blending and coupling effects is identified that shows desirable optical trapping in dielectric region and slight dispersion over a wide incident angle range while maintaining an average absorption greater than 90%

Summary

Introduction

On the other hand, based on their strong light concentration and scattering properties, light-trapping layers employing metallic plasmonic microstructures have gained significant attention recently[1,2,13,14]. Compared to elaborate periodic microstructures, random microstructures usually require relatively simple and low-cost fabrication methodologies, and their optical properties are expected to be less susceptible to imperfections Colloidal microspheres and their corresponding arrays are effective platforms to realize light-trapping by excitations of the localized resonances and coupled guided modes[38,39,40]. By optimizing the structural parameters of the absorber, such as the mixture ratio of these two different-sized microspheres and the thickness of the metallic cap over the PS beads, an ultra-broadband infrared absorption arising from effective modes blending and coupling effects is identified that shows desirable optical trapping in dielectric region and slight dispersion over a wide incident angle range while maintaining an average absorption greater than 90% In principle, this absorption band can be scaled over a wide frequency range by tuning the PS colloids sizes. This work offers a facile and cost-effective strategy to fabricate an ultra-broadband perfect absorber with a very large area, and it demonstrates great potential for applications in optoelectronic devices based on high-efficiency light-harvesting

Methods

Results

Conclusion