Bistable polarization switching in transverse magnetic wave-injected semiconductor lasers by mode hopping

Bistable optical switching, which is applicable to optical memory, is a key technology for the optical information-processing system. This paper describes the polarization switching of a semiconductor laser whose normal and inverted output could be obtained simultaneously. This bistability is realized by utilizing a semiconductor laser with bistable mode-hopping characteristics (master laser) and injecting the TM polarization output of this laser into another semiconductor laser (slave laser) constantly biased to the oscillation threshold. It is proposed and confirmed by experiment that, by assuming these two lasers as one optical system, bistable polarization switching can be obtained between the injection current of the system and the output polarization of the system. First, as the principle of this polarization switching, the dependence of the injected light wavelength on amplification index of a semiconductor laser amplifier is explained. Then, the control of output polarization by TM wave injection and mode hopping of a laser is explained and the bistable characteristics of this optical system are discussed from experimental and simulation viewpoints based on these principles. The advantages of this bistable polarization switching are pointed out theoretically and experimentally, and the intensity difference of the ON/OFF output and the rotation direction of the bistable loop can be set according to the characteristics of the master and the slave laser. Moreover, the possibility of multislave connection is conjectured.