Spectral investigation of a large-area 2D silicon photonic crystal slab for mid-IR radiation

A two-dimensional silicon photonic crystal (PhC), which is designed to provide a modified dispersion for photon energies of less than half of the electronic band gap of silicon, and which has been fabricated by laser interference lithography (LIL), is studied by angular dependent infrared reflectivity measurements. The resonance features, which we observe in the polarized reflectivity spectra, and which arise from resonant coupling of the infrared radiation to the leaky modes, are used to derive the probed leaky modes' quality factor of the PhC fabricated by LIL. We also present photonic band structure calculations to reveal the bandgaps of the guided modes.