  We propose a scalable design for a spin-photon interface to a color center in
a diamond microdisk. The design consists of a silicon oxynitride hexagonal
lattice overlaid on a diamond microdisk to enable vertical emission from the
microdisk into low-numerical aperture modes, with quantum efficiencies as high
as 45\% for a tin vacancy (SnV) center. Our design is robust to manufacturing
errors, potentially enabling large scale fabrication of quantum emitters
coupled to optical collection modes. We also introduce a novel approach for
optimizing the free space performance of a complex structure using a dipole
model, achieving comparable results to full-wave finite difference time domain
simulations with a 650,000 times reduction in computational time.
