Speaker
Description
High quality single photon sources (SPSs) are extremely desirable in quantum information processing. In order to facilitate integration with existing silica fiber based photonic infrastructure, the SPS should emit photons in telecom spectral range where dispersion and propagation losses are the lowest. Such SPS can be realized in InAsP/InP quantum dot (QD) nanowires (NWs). Tailoring the NW geometry to couple QD spontaneous emission (SE) to a NW single optical mode results in lower in-plane losses and better upward collection of the SE into limited numerical aperture (NA) available experimentally [1]. In this material system, defect-free zinc blende structures can be grown using chemical beam epitaxy with great reproducibility, precision and control over both QD and NW parameters [2]. The aim of this work is to provide optimal NW design taking into account technological limitations and tolerances.
In our study, we model the emission of an electric dipole (simulating the QD) embedded in a single InP NW vertically grown on InP (100) substrate. The simulations were performed in commercial Ansys Lumerical software, using finite-difference time-domain method (FDTD). In the first step, the emission of the dipole, placed in an infinite square-based InP NW, was modeled as a function of NW shell thickness to find the estimated value for optimal optical confinement providing single mode propagation along the NW. In the next step, a realistic geometry of a square-based tapered NW was implemented. The simulations covered the optimization of the NW length and taper angle, QD position along the NW axis as well as fine-tuning of the NW shell thickness. The calculations focused on understanding the photon extraction efficiency upward within the most commonly used NA of 0.4 and 0.65 and the corresponding far-field pattern evaluated for the dipole emission using the reasonable parameter space achievable in this fabrication approach for NW growth. Next, by using a metallic mirror beneath the NW we provide optimized structure design with extraction efficiency as high as 39% for 1500 nm (NA of 0.65). The influence of a gold mirror under the NW was modelled using the PMC boundary condition. This contribution gives valuable feedback for guiding the growth of optimized structures and provides theoretical emission extraction efficiency, which could be compared afterwards to the experimental results.
We acknowledge financial support from the National Science Centre (Poland) within Project No. 2020/39/D/ST5/02952
[1] J. Claudon, N. Gregersen, P. Lalanne, J.M. Gérard, ChemPhysChem 14, 2393 (2013)
[2] G. Bucci, V. Zannier, F. Rossi, A. Musiał, J. Boniecki, G. Sęk, L. Sorba, ACS Appl. Mater. Interfaces 16, 26491 (2024)
