In this work, we numerically study the focusing of a linearly polarized laser beam of wavelength λ = 633 nm using microcubes of heights 0.4 µm, 0.6 µm, and 0.8 µm and width varying from 0.4 µm to 0.8 µm fabricated of silica (refractive index n = 1.46) on a substrate.
The minimal focal spot was obtained for microcube with height of 0.6 µm and width of 0.58 µm. The diameters of photonic nanojet in this case were equal to FWHMmin = 0.39λ and FWHMmax = 0.67λ.