Intersubband electro-optical modulators based on intervalley transfer in

Abstract

The present invention is an electro-optical modulator having (a) a first semiconductor layer and a second semiconductor layer; (b) a first quantum well layer having a conduction band minimum at an optically active point (typically the L point or the X point), disposed between the first and second semiconductor layers; (c) a second quantum well layer having a conduction band minimum at the optically inactive (at normal incidence) .GAMMA. point, disposed between the first and second semiconductor layers; (d) a spacer layer disposed between the first and second quantum well layers, where the spacer layer has a conduction band minimum that is large enough for establishing quantum confinement in the first quantum well layer at the optically active point and in the second quantum well layer at the .GAMMA. point, but small enough to allow tunnelling between the two layers on a time scale consistent with the desired switching response time. The invention also has some controllable means for applying an electric field. The invention can produce both intensity and phase changes, and may be used in a Fabry-Perot device to achieve greater modulation for a given active region thickness.