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AssigneeNorthrop Grumman Corporation
InventorsElizabeth T. Kunkee, David V. Forbes, David C. Scott, Timothy A. Vang, Wenshen Wang
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A coupled quantum well Mach-Zehnder modulator that employs a push-pull structure to reduce the modulation voltage. The Mach-Zehnder modulator includes a first arm having a first PIN semiconductor device and a second arm having a second PIN semiconductor device. The intrinsic layers of the PIN devices include a coupled quantum well structure to provide an opposite index of refraction change for different DC bias voltages. An RF signal used to modulate the light beam is applied to the two arms in phase and causes the index of refraction in the intrinsic layers of the two PIN devices to change in opposite directions so that a push-pull type drive is achieved without requiring 180° out-of-phase RF drive signal.
1 A semiconductor PIN Mach-Zehnder modulator for modulating an optical signal with an RF signal, said modulator comprising:
2 The modulator according to claim 1 wherein the coupled quantum well structures of the first and second PIN devices each have a well/barrier structure selected from the group consisting of InGaAs/InP, InGaAsP/InGaAsP, InGaAlAs/InP, GaAs/AlGaAs and InGaAlAs/InGaAlAs.
3 The modulator according to claim 1 wherein the modulator is an analog modulator that intensity modulates the optical signal with the amplitude of the RF signal.
4 The modulator according to claim 1 wherein the first and second DC bias signals are different.
5 A semiconductor PIN modulator for modulating an optical signal with an RF signal, said modulator comprising:
6 (Cancelled).
7 The modulator according to claim 5 further comprising 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 applying 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.
8 The modulator according to claim 7 wherein the first and second DC bias signals are different.
9 The modulator according to claim 5 wherein the coupled quantum well structures of the first PIN device has a well/barrier structure selected from the group consisting of InGaAs/InP, InGaAsP/InGaAsP, InGaAlAs/InP, GaAs/AlGaAs and InGaAlAs/InGaAlAs.
10 The modulator according to claim 5 wherein the modulator is an analog modulator that intensity modulates the optical signal with the amplitude of the RF signal.
11 A method of modulating an optical signal with an RF signal, said method comprising the steps of:
12 The method according to claim 11 wherein the steps of providing a first PIN device and a second PIN device include providing coupled quantum well structures in the intrinsic layers that have a well/barrier structure selected from the group consisting of InGaAs/InP, InGaAsP/InGaAsP, InGaAlAs/InP, GaAs/AlGaAs, and InGaAlAs/InGaAlAs.
13 The method according to claim 11 wherein the RF signal intensity modulates the optical signal.