Optical bistability in GaInAsP/InP coupled-circular resonator microlasers.

Optical bistability is realized in GaInAsP/InP coupled-circular resonator microlasers, which are fabricated by planar technology. For a coupled-circular resonator microlaser with the radius of 20 μm and a 2 μm-wide bus waveguide, hysteresis loops are observed for the output power coupling into an optical fiber versus the cw injection current at room temperature. The laser output spectra of the upper and lower states of the hysteresis loop indicate that the bistability is related to mode competitions. The optical bistability can be explained as the mode competition between the symmetry and antisymmetry coupled modes relative to the bus waveguide.