Enhanced quantum dots spontaneous emission with metamaterial perfect absorbers

Metamaterial perfect absorbers (PAs) made of a hexagonal array of holes on Ag-SiO ₂ -Ag thin films have been realized and utilized to enhance the spontaneous emission rate and photoluminescence intensity of CdSe/ZnS quantum dots (QDs) spin-coated on the absorber top surface. Perfect absorption of incoming light occurs at the wavelength where the impedance is matched to that of the free space. When QDs strongly excite both the electric and magnetic resonances at this perfect absorption wavelength, a significant Purcell effect on the spontaneous emission process and enhanced radiative outcoupling of photoluminescence intensity are expected. For perfect absorbers with near-unity absorption at the QD emission wavelength of 620 nm, 5-fold Purcell enhancement of the spontaneous emission rate and 3.6-fold enhancement of photoluminescence intensity are demonstrated in the time-resolved photoluminescence experiments, which are in good agreement with three-dimensional finite-difference time-domain simulation. These results will advance the understanding and applications of metamaterial PA-based light harvesting and emitting devices.