Bright Single Photon Emission from Quantum Dots Embedded in a Broadband Planar Optical Antenna

Abstract

Photonic structures capable of enhancing the light-outcoupling efficiency of embedded epitaxial quantum dots (QDs) in a broad spectral range are attractive for the realization of bright sources of single photons and entangled photon pairs. In this work, a planar-multilayer antenna is experimentally demonstrated for GaAs QDs embedded in AlGaAs membranes. The antenna consists of a metal (Au or Ag) reflector and a semi-transparent metal (Ag) director, with a thin oxide layer (hafnium dioxide (HfO2) or aluminium oxide (Al2O3)) between metal and semiconductor layers. Simulations using the 3D finite-difference time-domain (FDTD) method indicate a maximal efficiency of 43% (for collection optics with a numerical aperture (NA) of 0.85), a wavelength-dependent Purcell factor ranging from ≈0.7 to ≈1.45, strong directional emission characteristics, as well as a broad bandwidth of ≈30 nm. In the experiment, we find a Purcell factor compatible with the simulation results, a maximum collection efficiency as high as ≈19% and an ultralow multiphoton emission probability of 0.006 ± 0.005. The planar geometry, its compatibility with post-growth tuning methods, facile fabrication, broad spectral bandwidth, and achieved performance make the presented structure competitive for solid-state sources of quantum light.