A model system for photonic crystals: macroporous silicon

A review of the optical properties of 2D and 3D photonic crystals based on macroporous silicon is given. As macroporous silicon provides structures with aspect ratios exceeding 100, it can be consid-ered as an ideal 2D photonic crystal. Most of the features of the photonic dispersion relation have been experimentally determined and were compared to theoretical calculations. This includes transmission and reflection of finite and bulk photonic crystals and their variation with the pore radius to determine the gap-map. All measurements have been carried out for both polarizations independently since they decouple in 2D photonic crystals. Moreover, by inhibiting the growth of selected pores, point and line defects can be realized and the corresponding high Q microcavity resonances as well as waveguiding properties were studied via transmission. The tunability of the bandgap was demonstrated by changing the refractive index by liquid crystals as well as optically-injected free carriers. Finally different realiza-tions of 3D photonic crystals using macroporous silicon are discussed. In all cases an excellent agree-ment between experimental results and theory has been observed.