Optical Spectra of Composite One-Dimensional Photonic Crystals With Extended Stop Bands Based on a Si-Air Structure

The optical spectra of composite one-dimensional photonic crystals (1-D PCs), fabricated by microstructuring of Si, are investigated. The composite PC is based on a Si-air structure and consists of two periodic 1-D PCs with various lattice constants a with a₁ = 2.7 μm and a₂ = 4 μm and various filling fractions f. The PCs are fabricated using photolithography followed by anisotropic chemical etching of (1 1 0) Si. Reflection and transmission spectra of this structure are measured using a Fourier transform infrared spectrometer combined with an IR microscope. The transmission spectra obtained demonstrate extended photonic stop bands (SBs), with characteristic transmission bands between the SBs. Theoretical and experimental transmission results indicate that the position of the extended SBs does not depend on the sequence of the individual PCs within the composite structure. In general, the calculated electric field distribution in the composite structure is similar to that of the individual PC components.