title: Near-perfect broadband absorption from hyperbolic metamaterial nanoparticles.
abstract: Broadband absorbers are essential components of many light detection, energy harvesting, and camouflage schemes. Current designs are either bulky or use planar films that cause problems in cracking and delamination during flexing or heating. In addition, transferring planar materials to flexible, thin, or low-cost substrates poses a significant challenge. On the other hand, particle-based materials are highly flexible and can be transferred and assembled onto a more desirable substrate but have not shown high performance as an absorber in a standalone system. Here, we introduce a class of particle absorbers called transferable hyperbolic metamaterial particles (THMMP) that display selective, omnidirectional, tunable, broadband absorption when closely packed. This is demonstrated with vertically aligned hyperbolic nanotube (HNT) arrays composed of alternating layers of aluminum-doped zinc oxide and zinc oxide. The broadband absorption measures >87% from 1,200 nm to over 2,200 nm with a maximum absorption of 98.1% at 1,550 nm and remains large for high angles. Furthermore, we show the advantages of particle-based absorbers by transferring the HNTs to a polymer substrate that shows excellent mechanical flexibility and visible transparency while maintaining near-perfect absorption in the telecommunications region. In addition, other material systems and geometries are proposed for a wider range of applications.
authors.affiliation: Department of NanoEngineering, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Conor T
authors.initials: CT
authors.lastname: Riley
authors.affiliation: Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Joseph S T
authors.initials: JS
authors.lastname: Smalley
authors.affiliation: Department of NanoEngineering, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Jeffrey R J
authors.initials: JR
authors.lastname: Brodie
authors.affiliation: Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, CA 92093.|Materials Science and Engineering, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Yeshaiahu
authors.initials: Y
authors.lastname: Fainman
authors.affiliation: Department of NanoEngineering, University of California, San Diego, La Jolla, CA 92093; zhaowei@ucsd.edu dsirbuly@ucsd.edu.|Materials Science and Engineering, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Sirbuly
authors.affiliation: Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, CA 92093; zhaowei@ucsd.edu dsirbuly@ucsd.edu.|Materials Science and Engineering, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Zhaowei
authors.initials: Z
authors.lastname: Liu
keywords: hyperbolic metamaterials; nanoparticle; nanowire; perfect absorber; photonic hypercrystal