Enhancing spontaneous emission rates of molecules using nanopatterned multilayer hyperbolic metamaterials

Abstract

Plasmonic nanostructures have been extensively used to manipulate the spontaneous light emission rate of molecules and their radiative efficiency. Because molecules near a metallic surface experience a different environment than in free space, their spontaneous radiative emission rate is generally enhanced. Such enhancement, measured by means of the Purcell factor, arises as a consequence of the overlap between the surface plasmon mode frequency and the emission spectrum of the molecule. However, such overlap is available only for a few narrow bands of frequency due to the limited plasmonic materials existing in nature. Although this limitation can be overcome by using hyperbolic metamaterials (HMMs)—a type of nanoscale artificial material with hyperbolic dispersion relations—the Purcell factor and the radiative power have remained relatively low. Here, we show that by nanopatterning a hyperbolic metamaterial made of Ag and Si multilayers, the spontaneous emission rate of rhodamine dye molecules is enhanced 76-fold at tunable frequencies and the emission intensity of the dye increases by ~80-fold compared with the same hyperbolic metamaterial without nanostructuring. We explain these results using a dynamic Lorentzian model in the time domain.

Visible-frequency asymmetric transmission devices incorporating a hyperbolic metamaterial

“…These materials offer an efficient way to manipulate the propagation of light to yield a number of novel and exotic phenomena, such as, negative refraction [19][20][21][22][23] , super-resolution imaging [24][25][26] , enhanced optical absorption 27,28 and spontaneous emission 29,30 . In this work, we leverage a visible-frequency hyperbolic metamaterial to implement a planar device of wavelength-scale thickness able to enforce highly asymmetric, broadband transmission of transverse-magnetic (TM) polarized visible-frequency light under illumination at normal incidence.…”

Field-effect induced tunability in hyperbolic metamaterials

“…We model ITO with a Drude model, which provides an adequate and accurate description of its permittivity in the visible-IR regime [32,33,39,41,42]. ITO can be heavily doped using rf sputter deposition, yielding a carrier concentration in the range 10 19 − 10 21 / cm 3 with a plasma frequency in the infrared range. Following previous experimental results [32,33,39,43], we investigate here ITO with background carrier concentration of 5 × 10 20 / cm Active tunability of the carrier concentration of ITO in metal-oxide-semiconductor (MOS) structures by up to two orders of magnitude has been reported previously [32,33,34,40,41].…”

“…Hyperbolic metamaterials are a special class of metamaterials with uniaxial anisotropy and effective parameters of opposite signs along different coordinate directions [8,9]. Such systems are being intensively studied because they exhibit diverging density of states, enabling extreme Purcell factors to be achieved [10], and support negative refraction of power [8]. They are also being investigated for emissivity control engineering for solar energy applications [11,12].…”

Highly efficient second harmonic generation in hyperbolic metamaterial slot waveguides with large phase matching tolerance

“…The hyperbolic metamaterials (HMs), which are consisted of layered metal-dielectric structures or nanowire arrays, have drawn significant interest very recently [16][17][18][19][20][21][22]. The HM display open-curved hyperbolic dispersion, which originates from one of the principal components of their electric effective tensor having the opposite sign to the other two [23].…”