Two-dimensional Penrose-tiled photonic quasicrystals: diffraction of light and fractal density of modes

We report measurements of the diffraction pattern of a two-dimensional photonic quasicrystal structure. Using a set of plane waves defined by the diffraction pattern we introduce a theoretical approach for the calculation of the band structure which captures the rotational and inflational properties of the quasicrystal. Based on this model we rnd that the density of modes of the quasicrystal displays a fractal character and a depleted region analogous to the band gap in a periodic system.