Science Advances reports photon extraction

Science Advances on May 20 published a paper describing a way to pull light more efficiently from quantum emitters buried inside bulk semiconductors, a longstanding obstacle for quantum photonics. The study, “Probing individual quantum emitters in bulk semiconductors via photonic nanojets,” used inverse-designed structures etched directly into high–refractive index materials to improve both excitation and collection of photons. The authors tested the approach on negatively charged nitrogen-vacancy, or NV, centers in diamond at room temperature. Science Advances highlighted the paper in a May 20 social-media post linking to the journal entry. ### Why is photon extraction from bulk materials a problem in the first place? Solid-state quantum emitters are promising components for quantum information processing, telecommunications and sensing, but the paper says their host materials often trap much of the emitted light because of their high refractive index. That means researchers can have a useful emitter in a bulk crystal and still struggle to get enough photons out to read or use it efficiently. (science.org) The authors also wrote that isolating a single emitter inside bulk material usually requires very pure samples and precise defect placement, which adds fabrication complexity. In many systems, randomly distributed emitters and background photoluminescence can further reduce signal quality. ### What did the researchers build instead of using conventional structures? The paper says the team used free-form topology optimization to design broadband monolithic photonic structures inside high-index materials containing relatively dense ensembles of randomly distributed quantum emitters. (science.org) Those structures generate tightly confined “photonic nanojets,” which are highly focused light fields that can selectively excite emitters and help direct emitted photons outward. The devices were fabricated with what the authors described as standard top-down patterning techniques. The study says the optimized geometries also suppressed background photoluminescence from near-surface defects and from other emitters deeper in the bulk, improving signal-to-noise performance. ### What were the main results in diamond? The demonstration used NV centers in a low-cost diamond sample at room temperature. (science.org) In that setup, the authors reported selective single-emitter excitation with a 10-fold power enhancement and more than 15-fold improvement in photon extraction efficiency for photoluminescence collection in confocal microscopy. Those numbers matter because NV centers are a widely studied defect platform for quantum sensing and quantum information experiments. (science.org) The paper says diamond-hosted NV centers can support optical readout and coherent control of spin states, including at room temperature. ### Why does the paper stress “bulk” semiconductors and not just nanostructures? The study focuses on emitters embedded in bulk substrates rather than emitters that must first be moved into thin membranes or highly customized nanophotonic devices. (science.org) The authors present the method as a route to accessing emitters in relatively dense, randomly distributed material while still using monolithic structures patterned into the host itself. That makes the work different from approaches that depend on precise placement of a single defect in a tightly engineered cavity. The paper says the same nanojet-generating concept could extend beyond NV centers and other diamond emitters to other semiconductor materials, and could also be generalized to fiber-integrated platforms. ### What comes next from here? The article was accepted on April 15, 2026 and published on May 20, 2026 in Science Advances under DOI 10.1126/sciadv.aea5936. (science.org) The paper says all data and code needed to reproduce the results are in the article or supplementary materials, and that experimental data are also available through a Zenodo record.