Towards Integrated and High Performance III-V/Si Laser for Analog Radio Over Fiber

The need for highly integrated system design for Analog Radio over Fiber (ARoF) architecture has long been identified as a solution to improve its noise figure and dynamic range. While silicon photonics has been the major technology driving this solution with several demonstrations of integrated filters, photodiodes, and amplifiers, etc., effective laser integration with silicon photonics has only recently found a way out through heterogeneous integration of III-V materials on Silicon (III-V/Si) substrate. With the laser integration access on this technology, an optimised design is needed to ensure its compliance with sensitive applications such as ARoF in both static and dynamic behaviours. In view of this, the path to better performance of heterogeneous III-V/Si laser through integrated extended cavity and enhanced optical mode confinement factor are highlighted in this article. Four laser chips are characterized and compared to study how differences in confinement factor and extended cavity configuration could influence the output power, wavelength tunability and Relative Intensity Noise (RIN). Two different configurations of integrated extended cavities, achieved with Sagnac mirrors and micro-ring resonators based Vernier filter, are presented and the confinement factor variation was achieved by changing the Si waveguide width. The presented measurement results show that a small integrated laser diode with an output power of similar to 5mW and tunable wavelength range up to 48nm , has reduced RIN property below -140 dB/Hz which is a key performance index for ARoF applications.