Locally deformed-ring hybrid microlasers exhibiting stable unidirectional emission from a Si waveguide.

We propose and demonstrate a locally deformed-ring (LDR) hybrid microlaser to realize stable unidirectional emission from a silicon waveguide. The coupled modes eliminate the competition between clockwise (CW) and counter-clockwise (CCW) modes, and the highly unidirectional characteristics are achieved with an enhanced mode quality factor based on a locally deformed notch in the LDR resonator. Using a divinylsiloxane-benzocyclobutene bonding technique, a LDR hybrid microlaser is fabricated vertically coupled to a silicon waveguide with a radius of 20 µm, a ring width of 4 µm and a notch width of 500 nm. The threshold current is 7 mA, and single-mode lasing is achieved with the side-mode suppression ratio of 27 dB. Nearly total unidirectional output from the CCW direction of a Si waveguide is demonstrated with a unidirectional ratio of 0.053.

Hybrid spiral-ring microlaser vertically coupled to silicon waveguide for stable and unidirectional output.

A hybrid spiral-ring laser vertically coupled to a silicon waveguide is demonstrated to achieve stable and unidirectional output theoretically and experimentally. The mode competition between clockwise (CW) and counter-clockwise (CCW) modes is eliminated due to the mode coupling in a spiral resonator. The simulation results indicate that the CCW and CW direction traveling waves are dominant components, respectively, for the spiral resonator without and with an output waveguide. A hybrid AlGaInAs/Si spiral-ring laser is designed and fabricated vertically coupled to a silicon waveguide. For a spiral-ring laser with a radius of 30 µm and a ring width of 5 µm, the continuous-wave lasing threshold of 9.5 mA is obtained with the threshold current density of 1.1 kA/cm(2) at a temperature of 285 K. The output power fluctuations due to the mode competition between CW and CCW modes are eliminated. The output power from CCW direction is five times that from CW direction.

Mode selection in square resonator microlasers for widely tunable single mode lasing.

Mode selection in square resonator semiconductor microlasers is demonstrated by adjusting the width of the output waveguide coupled to the midpoint of one side. The simulation and experimental results reveal that widely tunable single mode lasing can be realized in square resonator microlasers. Through adjusting the width of the output waveguide, the mode interval of the high-Q modes can reach four times of the longitudinal mode interval. Therefore, mode hopping can be efficiently avoided and the lasing wavelength can be tuned continuously by tuning the injection current. For a 17.8-µm-side-length square microlaser with a 1.4-µm-width output waveguide, mode-hopping-free single-mode operation is achieved with a continuous tuning range of 9.2 nm. As a result, the control of the lasing mode is realized for the square microlasers.