High-Power Long-Waveguide 1300-nm Directly Modulated DFB Laser for 45-Gb/s NRZ and 50-Gb/s PAM4

A 1300-nm high-speed high-power directly modulated distributed-feedback laser using floating feeding electrode has been demonstrated. A 5-μm-thick benzocyclobutene was used for planarization to float a coplanar waveguide, connecting a reversed-mesa ridge waveguide of a laser. Low parasitic capacitance was then formed. A long waveguide can thus be fabricated with low roll-off at high-frequency modulation, further enabling high-output optical power. A 250-μm-long waveguide was fabricated, leading to >28-mW optical power with linear operation and -3-dB bandwidth of 26 GHz. Furthermore, improvement in high-frequency regime and the reduction near resonance peak were found, attaining a broadband and flat frequency response at high current. A 45-Gb/s non-return-to-zero and 50-Gb/s four-level pulse amplitude modulation with 35-km fiber transmission were successfully shown through modulating high-output optical power.