The final etch depth is here shorter than the initial etch, x max = 7.3 µm down from x max = 12.5 µm. As the 3D inverse woodpile photonic crystals or interest have a depth of x max = 7.7 µm, which is much greater than the characteristic Bragg length of 0.3 µm, even the reduced depth is plenty sufficient for the desired application, with a majority of the length of the crystal etched. The final etch is much closer to the desired perfect cylinder and suitable for photonic crystal applications.