Mode Characteristics and Optical Bistability for AlGaInAs/InP Microring Lasers

Mode characteristics and optical bistability are investigated for an AlGaInAs/InP microring laser, with an outer radius of 10 μm and a ring width of 3 μm, connected with a 2-μm-wide radial output waveguide. A clockwise bistable hysteresis loop is observed with the continuous injection current from 20 to 28 mA at 289 K, measured through a single-mode optical fiber coupled to the output waveguide in the center position. The lasing spectra with main lasing wavelength difference of 0.022 nm are observed for the upper and lower states of the hysteresis. Furthermore, an anticlockwise bistable hysteresis loop is observed as the fiber is moved away from the center of the output waveguide to the secondary peak position of the coupled power. Comparing the experimental and simulation results, we attribute the bistability to the mode competitions between the near-degenerate symmetric and antisymmetric modes with different far-field emission characteristics.