Although silicon-on-insulator (SOI) modulators have been demonstrated for future on-chip integrated-photonics interconnect architectures, they require an external laser source and suffer from unavoidable tradeoffs in operation bandwidth, footprint, drive voltage, extinction ratio, and/or insertion loss. To avoid these tradeoffs, researchers at Eindhoven University of Technology (Eindhoven, the Netherlands), Ghent University (Ghent, Belgium), and the Institut des Nanotechnologies de Lyon (Ecully, France), collaborating within the framework of the ICT-FP7 project HISTORIC, have demonstrated for the first time how the direct modulation bandwidth of an indium phosphide (InP) disc laser—fabricated using CMOS-compatible techniques—is dramatically enhanced to a 15 GHz, 3 dB modulation bandwidth while consuming only 1 mW of power.
Optical injection locking is achieved by using two lasers designated master and slave. When the master laser’s light matches the wavelength of the slave laser, it provides it with a “photon bias” so that turning it on and off produces fewer oscillations, significantly improving the direct-current modulation bandwidth. The 20 Gbit/s directly modulated disc laser consumes only 50 fJ/bit energy and has a low drive voltage (a few hundred millivolts) that is compatible with future CMOS logic-level voltages. Even though the slave laser is currently external to the chip, the results are a promising step toward a fully integrated high-speed optical interconnect transmitter that will eventually include these two (master and slave) disc lasers simultaneously integrated on CMOS.
Contact Oded Raz at [email protected].