Electrooptical effects in silicon

A numerical Kramers-Kronig analysis is used to predict the refractive-index perturbations produced in crystalline silicon by applied electric fields or by charge carriers. Results are obtained over the 1. 0-2. 0 m optical wavelength range. The analysis makes use of experimental electroabsorption spectra and impurity-doping spectra taken from the literature. For electrorefraction at the indirect gap, we find n = 1. 3 10^5 at = 1. 07 m when E = 10^5 V/cm, while the Kerr effect gives n = 10^-6 at that field strength. The charge-carrier effects are larger, and a depletion or injection of 10 18 carriers/cm 3 produces an index change of 1. 5 10^-3 at = 1. 3 m.