Lateral quantum-confined stark effect for integrated quantum dot electroabsorption modulators

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Date
2025
Authors
Murphy, Tommy
Broderick, Christopher A.
Peters, Frank H.
O'Reilly, Eoin P.
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Institute of Electrical and Electronics Engineers Inc.
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Abstract
Advances in III-V on Si quantum dot (QD) growth have enabled monolithic integration of high-performance electrically-pumped lasers on Si, as an enabling component for Si photonics. Another critical component is the electroabsorption modulator (EAM), which exploits the quantum-confined Stark effect (QCSE) to achieve high-speed modulation of laser signals. Conventional quantum well (QW) EAMs exploit a "vertical"QCSE via top and bottom electrical contacts. Rapid advancements in planar photonic integrated circuit technology motivate development of laterally-contacted EAMs, which offer benefits including reduced parasitic capacitance. The QCSE cannot be achieved via a lateral field in a QW, but can in a QD due to the three-dimensional carrier confinement. Here, theoretical analysis of the lateral-field QCSE in 1.3 μm InxGa1-xAs/GaAs QDs is undertaken. Comparing the QCSE produced by vertical and lateral electric fields for realistic QD morphology a robust lateral-field QCSE is demonstrated, with the optical absorption edge redshifting more rapidly vs. field strength than in a conventional QW-EAM. It is shown that lateral-field QD-EAM performance is expected to be strongly sensitive to the spectral linewidth of the band edge absorption, and can also depend upon the in-plane orientation of the lateral electric field. The impact of QD morphology - the base shape, aspect ratio and composition profile - is also quantified. It is demonstrated that InxGa1-xAs/GaAs QDs possessing high aspect ratios and low absorption linewidths are well-suited to develop lateral-field QD-EAMs. This suggests leveraging III-V on Si epitaxy to integrate EAMs with lasers or single-photon sources to realize high-speed Si photonic integrated circuits for applications in datacomms and linear optical quantum computing.
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Keywords
Electroabsorption modulators (EAMs) , Integrated photonics , Quantum dots , Quantum-confined Stark effect (QCSE) , Silicon photonics
Citation
Murphy, T., Broderick, C. A., Peters, F. H. and O'Reilly, E. P. (2025) 'Lateral quantum-confined stark effect for integrated quantum dot electroabsorption modulators', IEEE Journal of Selected Topics in Quantum Electronics, 31(5), 1900310 (10pp). https://doi.org/10.1109/JSTQE.2025.3552024
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