Photonically Integrated Gain-Switched Lasers For Optical Frequency Comb Generation

The authors present the complete characterization of two cost-efficient photonically integrated slotted lasers that offer regrowth free manufacturing. Furthermore, the application of these devices, as multi-carrier transmitters is also investigated. In particular, the authors employ gain switching, an optical frequency comb (OFC) generation technique based on the direct modulation. The first device used is a dual section discrete mode index patterned device. It comprises two sections, implemented in a master-slave configuration to achieve optical injection locking (OIL) of the slave section. The second, a four-section device, consists of two regrowth-free Fabry-Perot lasers, also forming a master-slave configuration. The authors demonstrate that the additional sections give finer control over the OIL parameters of the device. Results show that the OIL leads to the enhancement of the modulation bandwidth, which in turn can be used to generate a broader OFC. The generated OFC is characterized to demonstrate additional improvements brought by OIL such as reduced optical linewidth and relative intensity noise. The lower fabrication cost of such photonically integrated slotted lasers, accompanied by their applicability to OFC generation make them attractive potential candidates for the employment in next generation short reach optical networks.