Hybrid Deformed-Ring AlGaInAs/Si Microlasers With Stable Unidirectional Emission

Hybrid deformed-ring microlasers are investigated to realize stable unidirectional emission from a silicon waveguide. Based on numerical simulations of a finite-element technique, we compare directional emission characteristics for spiral microring lasers and locally deformed microring lasers with a notch or a protruded notch. The mode coupling can eliminate mode competition between clockwise (CW) and counterclockwise (CCW) propagating modes and result in better stable unidirectional emission for locally deformed microring lasers with a notch. For a hybrid spiral-ring microlaser with a radius of 30 μm and a ring width of 5 μm, we obtain the output power from the CCW direction as five times as that from the CW direction. The output power from CCW direction as nineteen times as that from CW direction is realized for a deformed-ring microlaser with a radius of 20 μm, a ring width of 4 μm, and a protruded notch of 500 nm.