Modulation response measurements and evaluation of MQW InGaAsP lasers of various designs

Abstract
Results from modulation measurements of 40 high-speed multi quantum well (MQW) lasers ((lambda) equals 1.55 micrometer) of various designs are presented. By fitting the careful calibrated measurements, both magnitude and phase, to an analytical transfer function we were able to determine if a certain laser was limited by thermal effects, parasitic-like effects, or nonlinear gain effects. We found that most of the devices in the study were limited by thermal effects and/or contact parasitics. The parasitics were found to be determined by the width of the high-doped contact layer and cladding layers below the metallic contact. It was also found that a high doping of the separate confinement heterostructure (SCH) layers decreases the damping of the relaxation peak since it facilitates the carrier transport. Improved contact design and high doped SCH-layers resulted in modulation bandwidths of around 24 GHz.

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