Operating regimes of single mode monolithic GaAs/AlGaAs semiconductor ring lasers

This paper reports on the fabrication and experimental characterization of index-guided semiconductor ring laser (SRLs) designed to operate on single transversal and longitudinal mode. Contrary to expectation, SRLs do not exhibit plain bidirectional CW operation for the two counterpropagating modes. Rather, they show an intricate and interesting regimes sequence, including, bidirectional operation with alternate harmonic oscillations, unidirectional CW operation, unidirectional operation with switchings between the modes.