Silica aerogel in optical fibre devices

Silica aerogel is a very light and highly porous form of silica glass, with densities and refractive indices much lower than those of ordinary solids. We describe optical interactions with aerogel surrounding tapered fibres or inside the holes of photonic crystal fibres. This enables a new class of fibre devices exploiting the properties of the aerogel as a rigid yet porous replacement for air, as a nonlinear medium and as a host for dopants. Examples include a stable package for fused couplers, a gas sensor and a nonlinear light source.