A direct comparison between heterogeneously integrated widely-tunable ring-based laser designs

Four ring-based tunable laser structures are firstly demonstrated in the heterogeneous integrated silicon platform. Except for double-sided coupled-ring structure, the other three ones show comparable narrow-linewidth (∼200kHz) and output power (∼10mW) across entire wide-tuning ranges (∼40nm) with high side-mode suppression ratio (>40 dB).