Figure 2From: Silicon-based photonic crystals fabricated using proton beam writing combined with electrochemical etching methodTitled scanning electron microscope images of silicon pillars in square lattice. (a) Period of 2 μm with a large r/a ratio, where r is the radius of the pillars and a is the lattice period. (b) Period of 4 μm with a small r/a ratio.Back to article page