Characterisation of strained (111)B InGaAs/GaAs quantum well lasers with intracavity optical modulator

Abstract

We have studied InGaAs/GaAs quantum well (QW) lasers with an intracavity saturable absorber grown on (111)B GaAs. The effect of the built-in piezoelectric field, resulting from strained growth, on the gain/absorption spectra is modelled theoretically and measured experimentally. With the piezoelectric field opposing and exceeding the intrinsic field in our structure an externally applied reverse bias can be used to change the net-field in the well from forward to reverse via the flat-band condition. Changing the field in the QW of the passive section influences its absorptive behaviour, changing the light output characteristics. Large hysteresis loops in the light output versus current relation are observed which can be tailored by the applied bias. Additionally, the change in absorption with applied bias provides the possibility of integrated amplitude modulation, avoiding the direct modulation of the active section. An extinction ratio of −11dB was measured when changing the bias at the absorber by 1V.