Linear and nonlinear effects of light propagation in low-index photonic crystal slabs

We investigate theoretically and experimentally photonic crystals realised in slab waveguides made of materials with a low refractive index. Although in such systems a two-dimensional photonic bandgap for TE polarised light can be achieved, the low index imposes several restrictions influencing the performance. We investigate the transmission and dispersion properties of photonic crystal defect waveguides, high-quality factor microcavities and unusual phenomena of light propagation and localisation in truly periodic systems without defects. This is compared to results obtained in high-index materials. Furthermore we investigate theoretically frequency conversion and solitons in nonlinear photonic crystals. An optical parametric oscillator in a photonic crystal microcavity and strongly localised solitons in coupled microcavities are proposed.