2. Optical modulator by carrier depletion in silicon

2.1 Context

The refractive effects commonly used in optical modulators are the Pockels, Kerr and plasma effects. In a centro-symmetrical material like silicon, the Pockels effect does not exist, and the Kerr effect is very weak, even negligible. The most effective way of obtaining a rapid variation in the optical properties of silicon at optical telecommunications wavelengths (1.3-1.55 μm) is therefore to use the variation in refractive index by variation in free carrier density . Various solutions have been proposed in the literature to obtain this variation in silicon,...