Electroabsorption Modulated Laser Based on Identical Epitaxial Layer and Transmission Line Technology

Abstract

Low-cost solutions for delivering high communication bandwidths in both short- and long-haul systems are urgently required. Electroabsorption modulated lasers (EMLs), comprising a distributed feedback (DFB) laser and electroabsorption modulator (EAM), can address this. They are compact and offer a high modulation speed with low drive voltage, low chirp, and high extinction ratio [1] . To the best of our knowledge, the EAM in EMLs based on identical epitaxial layer technology has so far been configured with a lumped electrode. This can take the form of either a circular-pad, a rectangular-pad or the centre electrode of a ground-signal-ground (GSG) configuration. All result in a high capacitance, which in turn limits the modulation speed. Although the GSG choice has a similar configuration to that of a coplanar waveguide (CPW), it still behaves as a lumped electrode because of the lack of impedance matching. A planarized film of low- k material can be used to reduce the capacitance, however standard methods such as Benzocyclobutene or polyimide-based planarization are very difficult to implement as they are incompatible with many photonic integration steps [2] .