Hard Limiting Opto-electronic Logic Devices
We report the demonstration of two novel opto-electronic devices whose characteristics appear to make them suitable for optical logic. One of the devices may be developed into a NOR or NAND gate and the other into an OR or AND gate. The devices are based on the use of electronic gain together with optical input and output and the specific implementation uses a photo-transistor to provide photo-detection and gain and a GaAs/AlGaAs multiple-quantum-well (MQW) electro-absorption modulator  to enable optical output. The components are connected in such a way as to provide a characteristic suitable for logic : the output is hard-limited, the input is isolated from the output and the switching time is potentially fast, Electronic nonlinearities are strong, giving the potential for low power switching, and are fundamentally fast and optical access has the potential of high data rate communication with low crosstalk.
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