ScienceAdvances posts photon extraction study

Science Advances on May 20 pointed readers to a study on a stubborn quantum-hardware problem: how to get light out of dense bulk materials while still addressing one emitter at a time. The paper, published in 2026, describes inverse-designed photonic structures etched directly into high–refractive index materials to create “photonic nanojets” that can both focus excitation and improve collection of emitted photons. (x.com) The authors tested the approach in diamond, using negatively charged nitrogen-vacancy, or NV−, centers at room temperature. (science.org) They reported selective single-emitter excitation with a 10-fold power enhancement and more than 15-fold improvement in photon extraction efficiency in confocal photoluminescence collection. ### Why is photon extraction such a problem in bulk materials? Solid-state quantum emitters are used as single-photon sources and spin qubits for quantum information processing, telecommunications and sensing, the paper said. But the same bulk semiconductors that host those emitters often have high refractive indices, which trap much of the light and make photon collection inefficient. (x.com) The study also said isolating one emitter in bulk material usually requires high-purity samples and precise defect implantation. Those fabrication demands add complexity when researchers want scalable devices rather than one-off lab demonstrations. (science.org) ### What did the researchers build instead? The 2026 paper said the team used free-form topology optimization to design broadband monolithic photonic structures inside high-index materials containing relatively dense, randomly distributed emitters. Those structures were then fabricated with standard top-down patterning techniques. The resulting devices generate tightly confined photonic nanojets — concentrated optical fields that the authors said enable selective excitation of individual emitters while also improving photon extraction. (science.org) The paper said the optimized geometries also suppress background photoluminescence from near-surface defects and other emitters in the bulk, raising the signal-to-noise ratio. ### What was the proof-of-concept system? The paper used NV− centers in a low-cost diamond sample as its case study. NV centers in diamond are a common platform because they allow optical readout and coherent control of spin states, and can operate at room temperature, according to the article. (science.org) The supplementary materials said the nanojet design was optimized to remain broadband across the NV fluorescence bandwidth at room temperature. The authors also modeled Purcell enhancement by treating the color centers as electric dipoles at experimentally relevant depths and comparing radiated power with and without the nanojet structure. (science.org) ### What is new here compared with surface-friendly emitter platforms? A longstanding advantage of two-dimensional materials is that their emitters sit close to accessible surfaces, which can make excitation and photon extraction easier. By contrast, the new study is aimed at bulk semiconductors, where emitters can be more protected but harder to reach optically. (science.org) The authors’ claim is that inverse-designed nanojets can narrow that gap for bulk systems by improving both access and collection without requiring ultraclean, sparsely populated samples. The paper said the method should extend beyond diamond to other semiconductor hosts and could be generalized to fiber-integrated platforms. (science.org) ### Where can readers find the study and what comes next? Science Advances listed the article as “Probing individual quantum emitters in bulk semiconductors via photonic nanojets,” with Behrooz Semnani and Michal Bajcsy as corresponding authors. The supplementary file is posted alongside the paper and details the topology optimization, simulation setup and broadband optical response used in the work. (arxiv.org) (science.org)