Optical modulators based on the Franz–Keldysh effect.

An electroabsorption Modulator is a Semiconductor device which can be used for controlling the Intensity of a Laser beam via an electric voltage. Its principle of operation is based on the Franz–Keldysh effect, i.e., a change in the Absorption Spectrum caused by an applied electric field, which changes the bandgap Energy but usually does not involve the excitation of carriers by the electric field.