40 GHz Actively Mode-Locked Distributed Bragg Reflector Laser Diode Module with an Impedance-Matching Circuit for Efficient RF Signal Injection

A 40 GHz actively mode-locked laser diode integrated with an electroabsorption modulator as a mode locker was developed. The laser was packaged in a module together with an impedance-matching circuit of double open stubs for efficient RF signal injection. A 13 dB improvement of the RF injection efficiency was successfully achieved compared with a conventional 50 Ω terminated circuit. Nearly transform-limited, picosecond (<3 ps) pulses were successfully generated with a low timing jitter of 0.15 ps. A wide locking bandwidth over 1.9 GHz (39 GHz–40.9 GHz) was achieved while retaining small variation of pulse widths and low relative intensity noise values of less than -130 dB/Hz. Such a wide locking range could fully cover an error in cavity length in the cleaving process and is very promising for cost-effective device fabrication.