Photoluminescence (PL) Imaging of QDs for Deterministic Fabrication of On-Demand Single-Photon Sources

Solid-state single-photon emitters are crucial for developing efficient on-chip quantum information processing platforms. Self-assembled semiconductor Quantum dots (QDs) are one of the promising solid-state quantum emitters for quantum information technologies such as quantum communication, quantum computation, quantum teleportation, optical quantum networks, and so on. Single photon emission from a single QD is quite an efficient process because of the quantized nature of the two-level system. However, collecting all these single photons for usable application is nearly impossible because the quantum dot emits randomly into different spatial modes. This problem is tackled by incorporating the QD within an engineered photonic structure. This configuration allows emission into only one single mode, leading to more efficient devices. While there is much success in designing high-performance photonic structures, one extremely challenging aspect is the spatial and spectral positioning of the QD within the structures. The QD growth by the self-assembly process results in randomly positioned QDs. In addition, the QDs come in different shapes and sizes, leading to different optical properties. These pose a significant challenge in fabricating photonic structures with aligned QD positions and spectra with the photonic structure. Over the years, different methods have been employed to determine each QD's exact position and spectrum on the sample and then effectively fabricate structures around the center. Methods like in-situ photolithography [1], In-situ cathodoluminescence [2], and two-color photoluminescence [3] have been widely used in the literature to develop efficient single-photon sources. However, most of these studies reported the fit uncertainties which is less significant compared to the large uncertainty of fabricating structures around the QD.