Single- and Twin-Photons Emitted from Fiber-Coupled Quantum Dots in a Distributed Bragg Reflector Cavity

In this work, we develop single-mode fiber devices of an InAs/GaAs quantum dot (QD) by bonding a fiber array with large smooth facet, small core, and small numerical aperture to QDs in a distributed Bragg reflector planar cavity with vertical light extraction that prove mode overlap and efficient output for plug-and-play stable use and extensive study. Modulated Si doping as electron reservoir builds electric field and level tunnel coupling to reduce fine-structure splitting (FSS) and populate dominant XX and higher excitons XX⁺ and XXX. Epoxy package thermal stress induces light hole (lh) with various behaviors related to the donor field: lh h₁ confined with more anisotropy shows an additional X_Z line (its space to the traditional X lines reflects the field intensity) and larger FSS; lh h₂ delocalized to wetting layer shows a fast h₂-h₁ decay; lh h₂ confined shows D_3h symmetric higher excitons with slow h₂-h₁ decay and more confined h₁ to raise h₁-h₁ Coulomb interaction.