C-band 33-GHz high flatness photon-photon resonance directly modulated semiconductor lasers

Directly modulated lasers (DMLs) based on photon-photon resonance (PPR) effect, termed PPR-DMLs, offer significant advantages in modulation bandwidth. However, the uncontrollable amplitude of the PPR leads to significant variations in the intensity response across frequencies, which degrades the broadband consistency of systems based on DMLs. We propose and experimentally demonstrate a new method to flatten the frequency response of InP-substrate-based PPR-DMLs, while preserving the modulation bandwidth. The realized high-flatness large-bandwidth directly modulated laser (HFLB-DML), operating at 1553.92 nm, achieves a ± 2 dB response flatness across 15-32 GHz, along with 12 mW output power and a 49 dB side-mode suppression ratio (SMSR). The research method in this paper demonstrates that the HFLB-DML exhibits an excellent flat frequency response exceeding 30 GHz, making it a highly promising candidate for broadband, high-fidelity microwave photonic systems.