Patent ID: 6836351
Filing Date: 2004-12-28
Classification: B82Y,G02F,H01L

Abstract:
An optical modulation apparatus for producing a laser beam modulated by a modulation signal, comprising:an interferometer having a beam splitter, first and second parallel optical branches fed by said beam splitter and a beam combiner fed by said first and second parallel optical branches; a laser for furnishing said laser beam to said interferometer, said laser having a laser wavelength; first and second optical phase shifters in respective ones of said first and second parallel optical branches, each one of said first and second optical phase shifters comprising: (a) an intrinsic semiconductor crystalline planar layer and p-type and n-type planar semiconductor layers on opposite faces of said intrinsic semiconductor crystalline planar layer, said intrinsic layer lying in a plane parallel to a direction of propagation of said laser beam in the respective optical branch; (b) plural layers of planar arrays of quantum dots in said intrinsic layer, said intrinsic layer having an absorption spectrum with a predominant peak, said peak being shifted from said laser wavelength such that said laser wavelength lies in one of plural regions of steepest change of a refractive index of said intrinsic layer as a function of wavelength; (c) a reverse bias D.C. voltage source connected across said p-type and n-type layers and having a bias voltage lying in one of plural regions of steepest change in said index of refraction as a function of wavelength; (d) a pair of modulation source terminals connected across said reverse bias D.C. voltage source whereby a modulation signal modulates the reverse bias voltage across said p-type and n-type layers.