Spectroscopy of photonic bands in macroporous silicon photonic crystals

Variable-angle reflectance performed on macroporous silicon photonic crystals yields the dispersion of two-dimensional photonic bands. A comparison with calculated optical spectra identifies the spectral structures, which mark the onset of a propagating photonic mode, as one-dimensional critical points. The experimental results agree with theoretical determinations of the reflectance and of the photonic-band dispersion in a wide energy range. A symmetry analysis yields the selection rules for excitation of photonic modes, which can be treated like elementary excitations of the crystal.