Inverse design code from Alan Zhan, Taylor K. Fryett, Shane Colburn, and Arka Majumdar, "Inverse design of optical elements based on arrays of dielectric spheres," Appl. Opt. 57, 1437-1446 (2018)
based on celes https://github.com/disordered-photonics/celes Egel A, Pattelli L, Mazzamuto G, Wiersma DS, and Lemmer U. CELES: CUDA-accelerated simulation of electromagnetic scattering by large ensembles of spheres, Journal of Quantitative Spectroscopy and Radiative Transfer 199C (2017) pp. 103-110.
L-BFGS-B-C https://github.com/stephenbeckr/L-BFGS-B-C