Effectiveness of thin films in lieu of hyperbolic metamaterials in the near field

Publication Year
2014

Type

Journal Article
Abstract
We show that the near-field functionality of hyperbolic metamaterials (HMM), typically proposed for increasing the photonic local density of states (LDOS), can be achieved with thin metal films. Essentially, relative to thin films, HMMs have a broader but weaker coupling to the high-wavevector states of near-field emitters, such that when integrated over wavevector the overall coupling of the two is essentially equivalent. We show analytically that properly designed thin films, of thicknesses comparable to the metal size of a hyperbolic metamaterial, yield a LDOS as high as (if not higher than) that of HMMs. We illustrate these ideas by performing exact numerical computations of the LDOS of multilayer HMMs, along with their application to the problem of maximizing near-field heat transfer, to show that thin films are suitable replacements in both cases.
Journal
PRL
Volume
112
Pages
157402