A Compact SOI-Integrated Multiwavelength Laser Source Based on Cascaded InP Microdisks

We report on the performance of a compact multiwavelength laser (MWL) source heterogeneously integrated with and coupled to a silicon-on-insulator (SOI) waveguide circuit. The MWL consists of four InP-based microdisk lasers, coupled to a common SOI wire waveguide. The microdisk lasers operate in continuous-wave regime at room temperature, with a threshold current around 0.9 mA and a waveguide-coupled slope efficiency of up to 8 $\mu$ W/mA, for a microdisk diameter of 7.5 $\mu$m. The output spectrum contains four laser peaks uniformly distributed within the free-spectral range of a single microdisk. While thermal crosstalk is negligible, laser peak output powers vary up to 8 dB for equal microdisk drive currents, as a result of loss due to coupling with higher order modes supported by the 1-$\mu$m-thick microdisks. This nonuniformity could be eliminated by reducing the microdisk thickness.