Luminescent hyperbolic metasurfaces

Abstract

When engineered on scales much smaller than the operating wavelength, metal-semiconductor nanostructures exhibit properties unobtainable in nature. Namely, a uniaxial optical metamaterial described by a hyperbolic dispersion relation can simultaneously behave as a reflective metal and an absorptive or emissive semiconductor for electromagnetic waves with orthogonal linear polarization states. Using an unconventional multilayer architecture, we demonstrate luminescent hyperbolic metasurfaces, wherein distributed semiconducting quantum wells display extreme absorption and emission polarization anisotropy. Through normally incident micro-photoluminescence measurements, we observe absorption anisotropies greater than a factor of 10 and degree-of-linear polarization of emission >0.9. We observe the modification of emission spectra and, by incorporating wavelength-scale gratings, show a controlled reduction of polarization anisotropy. We verify hyperbolic dispersion with numerical simulations that model the metasurface as a composite nanoscale structure and according to the effective medium approximation. Finally, we experimentally demonstrate >350% emission intensity enhancement relative to the bare semiconducting quantum wells.

Fundamentals and Applications of Metasurfaces

“…We have reviewed a few of the representative demonstrations of metasurface‐based devices such as wave plates, polarimetries, metalenses, metaholograms, and optical vortex converters, and these examples are listed in Table 3 - 6 . There are still many other aspects or applications not included here, such as nonlinear metasurfaces, hyperbolic metasurfaces, thin‐film metasurfaces, parity–time symmetry metasurfaces, etc. Thanks to the advances in nanofabrication technologies, these low‐cost, large‐area, and mass‐productive techniques have sped up the development of static metadevices and are gradually becoming mature.…”

Detection of optical activity with diode-integrated hyperbolic metasurfaces

“…For t = 70 nm, DOLT = 0.993 and T(TM) = 0.991, while for t = 210 nm, DOLT>0.999999 and T(TM) = 0.973 If the metal is deposited via sputtering, then selecting a thickness of 70 nm ensures a practically realizable aspect ratio of less than 3:1, assuming a 100 nm period with a ~75 nm Ag block and a ~25 nm air trench [8]. However, as shown in Section 3.3, a thicker HMS is desirable to mitigate errors in detection.…”

“…Because of losses, and possibly gain [8], in the constituent materials, the effective permittivity elements are generally complex, with the single and double primes denoting real and imaginary parts, respectively. Given the dispersion of the constituent metallic and dielectric materials, maximizing the LD of the HMS therefore consists of identifying the optimal values of the HMS parameters, ρ and the thickness, t. For a Type II HMS [8], in which ε' || >0 and ε' ┴ <0, as occurs for a Ag/air system in the visible and near-infrared, the effective refractive indices are given by…”

“…Given the dispersion of the constituent metallic and dielectric materials, maximizing the LD of the HMS therefore consists of identifying the optimal values of the HMS parameters, ρ and the thickness, t. For a Type II HMS [8], in which ε' || >0 and ε' ┴ <0, as occurs for a Ag/air system in the visible and near-infrared, the effective refractive indices are given by…”

“…However, lateral multilayer HMM of nanoscale thickness, also known as hyperbolic metasurfaces (HMS) [7], exhibit extreme anisotropy at normal incidence. For example, extreme linear dichroism (LD) at near-infrared frequencies was demonstrated in a luminescent HMS (LuHMS) based on indium gallium arsenide phosphide (InGaAsP) multiple quantum wells nanostructured with silver (Ag) [8].…”