Multistability of a semiconductor laser with integrated delayed optical feedback

A new regime reveals the operation, where optical feedback enables a semiconductor laser to operate in one of several stable states. An experimental device integrates the delayed optical feedback by using a passive waveguide and an amplifier section on the same chip as the distributed feedback (DFB) laser. Feedback phase and strength can be adjusted by applying a direct current to the passive and amplifier section, respectively. For the laser current I DFB biased closely above threshold, three continuous wave (cw) states spaced 0.4 nm apart from each other and having a different power were found to coexist for multiple ranges of amplifier I A and phase current I P .