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Description
Non-classical light sources find applications in various fields of quantum technologies, e.g., communication, cryptography, computation and imaging. Quantum dot-based (QD) sources with performance enhanced by photonic structures have proven proof-of-principle advantage in terms of non-classical light state quality. This still requires optimization in the data transmission telecommunication spectral range, in particular in the O- and C-band. Additional advantage of QDs is their compatibility with semiconductor growth and processing technologies enabling on-chip integration of different functionalities and potential scalability.
In this work exemplary InP-based QD-photonic structures differing in growth technique and design will be discussed. They all aim at high efficiency and quality non-classical light emission at telecom wavelengths, but with different approaches.
The first group are InAs(P) QDs in InP photonic nanowires grown by vapour-liquid-solid mode of chemical beam epitaxy [1]. Optimization of the growth parameters resulted in defect-free structures in zinc blende structure with spectral range of emission determined by QD material composition and height. The extraction efficiency is targeted by geometry of the nanowire providing additionally broadband, but moderate enhancement of the emission rate.
Similar approach of broadband operation is realized in the case of molecular beam epitaxy-grown InAs QDs on distributed Bragg reflector in a photonic mesa structure. With the optimized mesa design extraction efficiency of 13% has been achieved [2]. These emitters feature low probability of multiphoton events under non-resonant pulsed excitation [3] and are potentially interesting in view of generation of pairs of entangled photons due to low exciton fine structure splitting [4].
The most advanced sources are based on InAs/InP QDs grown by metalorganic chemical vapour deposition [5] in hybrid circular Bragg grating cavities. These are not only deterministically fabricated using microphotoluminescence mapping technique, but also feature Purcell enhancement of emission by a factor of 4 and emit indistinguishable photons [6]. Cavity-based approaches are typically narrow-band, but in the case of circular Bragg grating cavity design high Purcell factor and broadband operation are combined owing to small mode volume.
[1] G. Bucci et al., ACS Applied Materials & Interfaces 16, 26491 (2024).
[2] A. Musiał et al., Applied Physics Letters 118, 221101 (2021).
[3] A. Musiał et al., Advanced Quantum Technologies 3, 1900082 (2020).
[4] A. Kors et al., Applied Physics Letters 112, 172102 (2018).
[5] D. A. Vajner et al., ACS Photonics 11, 339 (2024).
[6] P. Holewa et al., Nature Communications 15, 3358 (2024).
