Quantum well optical tristate devices

Abstract

We demonstrate integrated quantum well tristate logic devices for possible use in bus architectures. The devices have two optical output beams which represent the logic state of the output data depending on their relative power. When the power in one output beam exceeds the other, the logic state is a logic one or zero depending on which beam has the largest optical power. When the power in both output beams is equal, the device is in a disabled state. These optical devices are analogous to the tristate devices often used in electronic buses, where each device can be actively on, actively off, or disabled, with, at most, one device on the bus active at a time. We show two methods of generating tristate data, one using tristate quantum well modulators and one using tristate self-electrooptic effect devices (SEEDs),1 and we demonstrate a simple optical bus consisting of three such devices. Finally, we comment on the limitations on the number of devices that can be connected to a bus of this type.