Patent ID: 6933583
Filing Date: 2005-08-23
Classification: G02F

Abstract:
1. A semiconductor PIN Mach-Zehnder modulator for modulating an optical signal with an RF signal, said modulator comprising: a substrate; a first PIN device formed on the substrate and including a P-type layer, an intrinsic layer and an N-type layer, said intrinsic layer of the first PIN device including a coupled quantum well structure, said coupled quantum well structure of the intrinsic layer of the first PIN device having an electro-refraction curve that includes both a positive and negative slope; a second PIN device formed on the substrate and including a P-type layer, an intrinsic layer and an N-type layer, said intrinsic layer of the second PIN device including a coupled quantum well structure, said coupled quantum well structure of the intrinsic layer of the second PIN device having an electro-refraction curve that includes both a positive and negative slope; a Mach-Zehnder interferometer including a first optical path and a second optical path, said intrinsic layer of the first PIN device being positioned in the first optical path and said intrinsic layer of said second PIN device being positioned in the second optical path; and a biasing system, said biasing system including a first DC bias source applying a first DC bias signal to the intrinsic layer of the first PIN device, a second DC bias source providing a second DC bias signal to the intrinsic layer of the second PIN device, and an RF signal source providing the RF signal in phase to the intrinsic layers of the first and second PIN devices, wherein the first DC bias signal causes the first PIN device to operate on one of the positive or negative slope of the electro-refraction curve of the intrinsic layer of the first PIN device so that the RF signal causes the index of refraction of the intrinsic layer of the first PIN device to change in one direction and the second DC bias signal causes the second PIN device to operate on the other of the positive or negative slope of the electro-refraction curve of the intrinsic layer of the second PIN device so that the RF signal causes the index of refraction of the intrinsic layer of the second PIN device to change in an opposite direction at a particular point in time so that the modulator operates in a push-pull manner, wherein the first and second DC bias signals are different.