Microscopic model of Purcell enhancement in hyperbolic metamaterials

Abstract

We study theoretically a dramatic enhancement of spontaneous emission in metamaterials with the hyperbolic dispersion modeled as a cubic lattice of anisotropic resonant dipoles. We analyze the dependence of the Purcell factor on the source position in the lattice unit cell and demonstrate that the optimal emitter position to achieve large Purcell factors and Lamb shifts are in the local field maxima. We show that the calculated Green function has a characteristic cross-like shape, spatially modulated due to structure discreteness. Our basic microscopic theory provides fundamental insights into the rapidly developing field of hyperbolic metamaterials.

Graphene-based tunable hyperbolic metamaterials and enhanced near-field absorption

“…In Section 4 we investigate the radiation of a dipole at the interface of a finite thickness HM and we show that the HM is able to enhance the total power radiated by several orders of magnitude, reporting an enhancement of 5 × 10 2 at 2 THz. We also show that most of the power is directed into the HM, offering a viable route for wide band and wide incidence-angle super absorption interfaces at far-infrared frequencies, as previously discussed in [3,9,13,42] for optical frequencies. We show that this large enhancement of power emission is associated to the wide spatial spectrum being able to propagate inside the HM, that would be otherwise evanescent in free space.…”

“…The wide spatial spectrum of propagation supported by these HMs can lead to novel phenomena as increasing the power emitted by imposed dipoles [3,8] or scattered by nanoparticles [3,9] on HM surfaces, and this power is mostly directed into HMs. This exotic property enables features like focusing with very subwavelength resolution [10,11], controlling absorption [12], enhancement of spontaneous emission [13], increasing the decay rate of emitters [6], designing quantum and thermal emitters [14]. HMs can also host backwards waves and thus they are utilized for achieving negative refraction as in [15].…”

Enhanced acoustic sensing through wave compression and pressure amplification in anisotropic metamaterials

“…However, n eff cannot be an arbitrarily large value. Note that the largest wave vector is determined as k z ¼ p/p, which corresponds to the boundary of the first Brillouin zone in periodic systems 36,39 . The maximum effective refractive index n max is therefore determined as n max ¼ k z /k air ¼ c air /2pf (c air is the sound speed in air), which is limited by the periodicity p of the metamaterial structure.…”

“…This gives rise to the field of anisotropic metamaterials, which enable flexible control of electromagnetic and acoustic waves for realizing functional devices with unique properties 22,23,28,[39][40][41] . Here we report a metamaterial-enhanced acoustic sensing system based on highly anisotropic acoustic metamaterials (see Fig.…”

Photonic spin Hall effect in hyperbolic metamaterials for polarization-controlled routing of subwavelength modes

“…In particular, when circularly polarized light interacts with specifically designed nanostructured metasurfaces that break spatial inversion symmetry, photons of different polarizations (optical spin) may take different trajectories, in close analogy to the spin Hall effect for electrons [7][8][9][10][11] . In terms of manipulation of emission properties, anisotropic metamaterials with hyperbolic isofrequency surfaces have been proposed for nonresonant enhancement of the spontaneous emission rate 13 , which are fundamentally limited only by the basic dimensionality of an artificial unit cell 14 and nonlocal effects 15 . Such anisotropic metamaterials have different signs of the longitudinal (e 8 ) and transverse (e > ) components of the effective permittivity tensor and have been realized as nanowire arrays 16 or layered metaldielectric structures 13 ( Fig.…”