Multistability in grating-tuned external-cavity semiconductor lasers

In this paper, we discuss the multistable state in a semiconductor laser that has an external-cavity grating system for the first time (to the best of our knowledge). We analyzed onset conditions and stable solution conditions of the multistability and bistability, and observed open- and closed-loop multistabilities. The properties of the multistable loops depend upon whether the internal facet reflectivity of the laser diode is larger or smaller than the external grating cavity reflectivity. This phenomenon directly reflects the intrinsic properties of the coherent interactions between the internal facet and the external grating cavity in the semiconductor laser diode. We experimentally observed the optical pulse-width memory effect in the external grating-tuned semiconductor lasers. Based upon this setup and results, a multistable optical logic device can be built with a carefully designed compound cavity semiconductor laser device