Theoretical study on high-speed modulation of Fabry-Perot and distributed-feedback quantum-dot lasers:: K-factor-limited bandwidth and 10 Gbit/s eye diagrams

This paper presents a theoretical study of the high-speed modulation response of Fabry-Perot (FP) and distributed-feedback (DFB) quantum-dot lasers based on the rate equation models, making reference to available experimental data. We show that the K-factor-limited maximum modulation bandwidth increases with the maximum optical gain and that there is an optimum cavity loss to maximize the bandwidth at a given maximum gain, enabling us to design the bandwidth of FP lasers as well as DFB lasers with and without a phase shift. We present modulation wave forms of FP quantum-dot lasers to indicate that the maximum modal gain of 30-40 cm(-1) is sufficient for 10 Gbit/s eye opening, which explains the recent success of 10 Gbit/s modulation of the quantum-dot laser with ten dot layers in the active region having the maximum modal gain of 35 cm(-1). We show a design for low-driving-current 10 Gbit/s operation by shortening the cavity length with the optimum cavity loss maintained by the high-reflectivity coating. (c) 2007 American Institute of Physics.