Figure 3: 2D calculated PBS for a structure based on a square mesh of dielectric veins with a width of 0 . 2 8 5 𝑎 , with the dielectric material being a PSi layer with 40% porosity ( 𝜀 = 4 . 8 4 ). Bands are plotted along high-symmetry lines of the Brillouin zone, where frequency is given in normalized units ( 𝑎 / 𝜆 ). The representation of 2D Brillouin zone and the schematic representation of 2D structure used for the calculations are shown in the inset of PBS.