Abstract
We report the use of epsilon near zero (ENZ) metamaterial to control spontaneous emission from Zinc-Oxide (ZnO) excitons. The ENZ material consists of alternating layers of silver and alumina with subwavelength thicknesses, resulting in an effective medium where one of the components of the dielectric constant approach zero between 370nm-440nm wavelength range. Bulk ZnO with photoluminescence maximum in the ENZ regime was deposited via atomic layer deposition to obtain a smooth film with near field coupling to the ENZ metamaterial. Preferential emission from the ZnO layer into the metamaterial with suppression of forward emission by 90% in comparison to ZnO on silicon is observed. We attribute this observation to the presence of dispersionless plasmonic modes in the ENZ regime as shown by the results of theoretical modeling presented here. Integration of ENZ metamaterials with light emitters is an attractive platform for realizing a low threshold subwavelength laser.
Highlights
Epsilon near zero (ENZ) metamaterials (MMs) are designed to have one or more components of the dielectric permittivity tensor approach zero for a desired wavelength region
We report the use of epsilon near zero (ENZ) metamaterial to control spontaneous emission from Zinc-Oxide (ZnO) excitons
The ENZ material consists of alternating layers of silver and alumina with subwavelength thicknesses, resulting in an effective medium where one of the components of the dielectric constant approach zero between 370nm440nm wavelength range
Summary
Epsilon near zero (ENZ) metamaterials (MMs) are designed to have one or more components of the dielectric permittivity tensor approach zero for a desired wavelength region. ENZ metamaterials in the near-UV to near-IR ranges were realized using metal-dielectric composites in nano-rod form [9], nano-spheroids [10], and lamellar multilayers [4,5] In these structures the zero of the dielectric permittivity can be tuned to a desired range by controlling the fill-fraction of the metal in the structure [11]. We observed an intensity reduction by a factor of ten, in comparison to a reference sample of ZnO grown on silicon (Si) substrate, due to preferential emission into the ENZ MM This preferential emission is attributed to slow modes governing the photonic density of states (PDOS) in the near zero regime
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