Analysis of dynamic, modulation, and output power properties of self-assembled quantum dot lasers

Abstract

Dynamic, modulation, and output power (OP) characteristics of In(Ga)As/GaAs self-assembled quantum-dot lasers (SAQDLs) using multi-mode and multi-population rate equations analysis considering nonlinear material gain and thermal carrier escape pathways to both wetting layer and barriers are presented. I show that despite of significant effect of nonlinear material gain on time evolution of photon population, it does not affect 3-dB modulation bandwidth (MB). Thermal carrier escape processes have minor declining effects on modulation properties at around room-temperature (RT) operation and higher. Although turn-on delay increases with enhancement of temperature, in some bias currents, there is a reverse jump which is due to thermal carrier escape to barriers. In addition, it is indicated that optimum bias current to maximize MB increases as temperature enhances and that more disk-like SAQDs may provide higher MBs. Variations of some key parameters, bias current or mean quantum-dot (QD) radius, provide similar changing patterns for both MB and OP. While altering most of key parameters, average QD height, QD coverage, stripe width of the laser cavity, and temperature, leads to a tradeoff between MB and OP for a specific interval of those parameters. I show that considering our purpose, which is the highest OP or MB, we can achieve maximum possible output designing key parameters. For the present device, optimizing structural parameters, MB about 14 GHz is achieved at around RT operation under the moderate bias current 10 mA, which can be improved up to 30 GHz with decreasing carrier capture time. The results presented here may be used for designing QD lasers suitable for optical telecommunication.