Mechanically encoded single-photon sources: Stress-controlled excitonic fine structures of droplet epitaxial quantum dots

Abstract

We present numerical investigations based on the Luttinger-Kohn four-band k · p theory and, accordingly, establish a quantitatively valid model of the excitonic fine structures of droplet epitaxial GaAs/AlGaAs quantum dots under uni-axial stress control. In the formalisms, stressing a photo-excited quantum dot is equivalent creating a pseudo-magnetic field that is directly coupled to the pseudo-spin of the exciton doublet and tunable to tailor the polarized fine structure of exciton. The latter feature is associated with the valence-band-mixing of exciton that is especially sensitive to external stress in inherently unstrained droplet epitaxial GaAs/AlGaAs quantum dots and allows us to mechanically design and prepare any desired exciton states of QD photon sources prior to the photon generation.

Wavelength extension beyond 1.5 µm in symmetric InAs quantum dots grown on InP(111)A using droplet epitaxy

“…Likewise, the single-hole spectra are numerically solved for the 4 × 4 Luttinger-Kohn Hamiltonian matrix H h = H k h + H h + V k h I 4×4 (See Ref. 15 for details). Based on the calculated single-electron and single-hole spectra, the exciton binding energy V eh can be estimated simply by the formalism in Ref.…”

“…( 1), which we determined by AFM statistical analysis. The calculation was based on the k.p perturbation method with threedimensional strain modeling (see supplementary information for details) 14,15 . The theoretical level series well reproduces the experimental spectral peaks.…”

“…Then, the single-electron spectra are numerically calculated by solving the Schrödinger equation for the single-band effective-mass Hamiltonian H e = p 2 /2m * e + V k e + V e using the finite difference method. Likewise, the single-hole spectra are numerically solved for the 4 × 4 Luttinger-Kohn Hamiltonian matrix 15 for details). Based on the calculated single-electron and single-hole spectra, the exciton binding energy V eh can be estimated simply by the formalism in Ref.…”

Effects of electrostatic environment on the electrically triggered production of entangled photon pairs from droplet epitaxial quantum dots

“…Likewise, for a slowly varying electric field, the yielded Hamiltonian to a positively-charged hole in a QD reads . The energies and wave functions of a single hole in the QD are obtained by numerically solving, , using the finite-difference method 46,47 .…”

“…In the numerical calculation, the matrix elements of e - h exchange interactions are divided in the long-ranged and short-ranged parts according to the averaged Wigner-Seitz radius, and computed separately following the methodology in refs 46,58 . The former is treated in the dipole-dipole interaction approximation and numerically integrated using trapezoidal rules and the graphics processing unit (GPU) parallel computing technique for numerical acceleration.…”