Quantum well optical tri-state devices.

We demonstrate quantum well tri-state logic devices for possible use in optical bus architectures. The device has 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 are equal, the device is said to be in a "disabled" state. These optical devices are analogous to the "tri-state" 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 this tri-state data, one using tri-state quantum well modulators and one using optical tri-state Self Electro-optic Effect Devices (SEEDs), and we demonstrate a simple optical bus consisting of two such devices. Finally, we comment on the limitations on the number of devices that can be connected to a bus of this type.