Hybrid optical bistability and optical logic gates with avalanche heterojunction phototransistor and semiconductor laser diodes

In this paper, we propose and demonstrate a new kind of optical bistable scheme which is based on an AHPT (avalanche heterojunction phototransistor) and an LD. The operating principles of the AHPT and the completed bistable devices are discussed in details. A simple assumption is made to simplify the analysis. When the AHPT-LD-BOD works in the steady state, it presents four operating modes, which are linear amplification, avalanche gain, optical bistability, as well as optoelectronic switching. When it is in the mode of the optical bistability, the critical triggering optical power is no more than 10 μW and the output power at ON state is larger than 1 mW. The ratio of the output optical power at ON state to that at OFF state is greater than 4 dB. Based on the good performance of the AHPT, we can realize five elementary optical logic gates, which are OR, AND, INVERTER, NOR, and NAND. The advantage of this kind of bistable system over the conventional ones is that neither external optical nor electrical feedback is needed. Therefore, it is possible and convenient to realize either monolithic or hybrid integration.