ABSTRACT
By the end of the 1950s, the effect of an electric field on the absorption spectrum of a semiconductor had been investigated by Franz [1958] and Keldysh [1958]. The net result is a red-shift of the absorption edge. Because of this shift, absorption can become significant under the application of an electric field at a wavelength where the semiconductor is normally transparent. These absorption
variations (electroabsorption) have been exploited to realize intensity modulators. However, these absorption variations are only moderate and relatively long waveguide devices have to be used in order to obtain a significant contrast ratio.
