Patent ID: 7457487

Claim:
An optical modulator comprising: an active region including one or more semiconductor quantum well structures, each comprising: a well layer having a composition Si 1-x Ge x , wherein x is selected such that an energy-momentum relation E w (k) of the lowest energy conduction band of the well layer at k=0 has a local minimum at k=0; a first barrier layer having a composition Si 1-y Ge y and disposed on a first side of the well layer, wherein y<x; and a second barrier layer having a composition Si 1-z -Ge z and disposed on a second side of the well layer opposite the first side, wherein z<x; an optical propagation path within said modulator from an optical input to an optical output, wherein said optical propagation path passes through said active region substantially in a plane of the quantum well structures; wherein an electric field responsive to an electrical input to the device is present in the active region; wherein an optical response of the active region for light propagating along said optical propagation path is capable of being altered by the electrical input.