Study of the quantum-confined Stark effect in an unbiased [111]-oriented multi-quantum well semiconductor optical amplifier

In this paper, we present a procedure and model for determining the electric field F-wq that governs the quantum-confined Stark effect (QCSE) in each quantum well of an unbiased [111]-oriented InGaAs/InGaAsP multi-quantum well semiconductor optical amplifier (MQW-SOA) with a p-i-n diode structure. For a given input power value, we estimated the electric field F-wq by substituting into simple theoretical expressions the experimentally determined output power, some structural parameters, and the voltage provided by a digital multimeter operating in diode test mode connected between the electrodes of the amplifier. The model results were used to estimate the Stark shift of the MQW-SOA excitonic resonances, which were blue-shifted by 5.21 meV when the input power was varied from -15.9 to 5.17 dBm. The excellent agreement between the experimental and calculated results allowed the validation of the model. To the authors' knowledge, this is the first time that it has been experimentally demonstrated the presence of excitonic resonances in an MQW-SOA and the blue shift that they exhibit when the input power alters the QCSE. Finally, we used our model to investigate the impact of simultaneously modifying the strain in the quantum wells and the p-i-n junction built-in electric field (F-pin) on the variability of F-wq with respect to the input power. In fact, for zero input power, by modifying F-pin,( )we compensate for the fluctuation that F-wq undergoes when the strain is altered. Every time the strain is changed, and F-wq is compensated, a new operating regime is obtained. We found that the larger the operating regime strain, the less input power is required to vary vertical bar F-wq vertical bar by a given amount. For the MQW-SOA used in this work, about half the input power would be required to induce a 1 MV/m change in vertical bar F-wq vertical bar if an operating regime with a strain of -1.52 replaced one with a strain of -1.33.

Automated summary

In this paper, a procedure and model for determining the electric field that governs the quantum-confined Stark effect in a multi-quantum well semiconductor optical amplifier were presented. The model accurately estimated the Stark shift of the excitonic resonances and demonstrated the presence of excitonic resonances in the amplifier. Additionally, the impact of modifying the strain in the quantum wells and the built-in electric field on the variability of the electric field was investigated.