C-Band Directly Modulated Lasers With Tunable Photon–Photon Resonance in InP Membrane

InP membrane directly modulated semiconductor lasers (DMLs) with photon-photon resonance (PPR) have a lot of potential to be used in short-range telecommunication systems due to their small footprint, high energy efficiency, and high modulation bandwidth. However, the stability of the S21 response in PPR-based devices is sensitive to precise phase-matching between the lasing mode and PPR mode. We designed, fabricated, measured, and analyzed a C-band DML with active phase-tuning achieved by a thermal phase shifter on top of a long passive waveguide. The phase shifter enables tuning of the PPR frequency in the range of 5 GHz resulting in the PPR peak power enhancement of 16 dB. We study the small-signal responses at different combinations of bias current and phase shifter current and show, that in some cases the phase shifter enables a bandwidth that cannot be achieved by sweeping the bias current. The laser dynamic behavior is simulated and the influence of the most important design and processing parameters on bandwidth is studied in detail.