A unified description of semiconductor lasers with external light injection and its application to optical bistability

A unified description for semiconductor lasers based from below to above threshold with external light injection is presented using small-signal analysis. The threshold of a semiconductor laser can be reduced by external light injection. The gain change of the laser due to external light injection reaches its maximum just at threshold. Optical bistability in a semiconductor laser is found to be varied continuously from below to above threshold. An analytical expression for the bistable loop bandwidth is presented. There is an optical bias for a laser to maximize the loop bandwidth for a fixed injection power. The results are in good agreement with experiments