Inherent bandwidth limits in semiconductor lasers due to distributed microwave effects

Abstract

This letter studies the inherent bandwidth limits in high speed semiconductor lasers caused by microwave signal propagation along the device. We show experimentally and theoretically that microwave propagation at high frequency is dominated by loss and slow wave effects. The primary conclusions from this study are (1) the standard treatment of a diode laser as a lumped electrical element is invalid above 25 GHz for device lengths on the order of 300 μm and (2) the frequency dependence of the microwave loss results in rolloff in the modulation response at high frequency. This roll off results in bandwidth degradation relative to the simplistic lumped element case and leads to new length and electrode considerations in the design of high speed lasers.