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Quantum cryptography and optical quantum computing require well-performing single and entangled photon sources, placing stringent demands on semiconductor quantum dots (QDs) embedded in microcavities such as circular Bragg grating (CBG) resonators [1,2]. Their low optical mode volume facilitates enhanced coupling between quantum dot and resonator. At the same time, it necessitates accurate placement of the QD with respect to the cavity center of Δs < 20 nm. A larger displacement will result not only in a reduced Purcell factor but also produce a pronounced polarization bias on the emitted single photons [3].
We present recent advancements in the deterministic placement of CBG around pre-characterized self-assembled semiconductor QDs. Using hyperspectral imaging, we achieve high spectral and spatial accuracy. The introduction of optical markers with periodic features significantly enhances the reliability of position determination. To further improve accuracy, we apply post-processing image correction algorithms that reduce distortions.
Our results demonstrate that the accuracy achieved meets the demanding requirements of QD-cavity integration. We assess accuracy and device yield through imaging test fields and micro-photoluminescence measurements on fabricated devices. We evaluate the resonator-induced Purcell enhancement by measuring the excitonic lifetimes before and after integration of the QD into CBG resonators. The observed polarization of emitted light is correlated with the spatial displacement of QDs relative to the CBG center, providing key insights into optimizing QD placement for quantum applications.
[1] M. Davanço et al., A circular dielectric grating for vertical extraction of single quantum dot emission. Appl. Phys. Lett. 99, 041102 (2011).
[2] H. Wang et al., On-demand semiconductor source of entangled photons which simultaneously has high fidelity, efficiency, and indistinguishability. Phys. Rev. Lett. 122, 113602 (2019).
[3] G. Peniakov et al., Polarized and Unpolarized Emission from a Single Emitter in a Bullseye Resonator. Laser Photonics Rev. 18, 2300835 (2024).
