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Laser writing of spin defects in nanophotonic cavities


High-yield engineering and characterization of cavity–emitter coupling is an outstanding challenge in developing scalable quantum network nodes. Ex situ defect formation systems prevent real-time analysis, and previous in situ methods are limited to bulk substrates or require further processing to improve the emitter properties1,2,3,4,5,6. Here we demonstrate the direct laser writing of cavity-integrated spin defects using a nanosecond pulsed above-bandgap laser. Photonic crystal cavities in 4H-silicon carbide serve as a nanoscope monitoring silicon-monovacancy defect formation within the approximately 200 nm3 cavity-mode volume. We observe spin resonance, cavity-integrated photoluminescence and excited-state lifetimes consistent with conventional defect formation methods, without the need for post-irradiation thermal annealing. We further find an exponential reduction in excited-state lifetime at fluences approaching the cavity amorphization threshold and show the single-shot annealing of intrinsic background defects at silicon-monovacancy formation sites. This real-time in situ method of localized defect formation, paired with cavity-integrated defect spins, is necessary towards engineering cavity–emitter coupling for quantum networking.

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Fig. 1: In situ laser-written cavity-integrated spin defects.
Fig. 2: Preservation of cavity-mode optical and spin signatures on irradiation with a single UV pulse.
Fig. 3: Lifetime analysis of laser-irradiated cavity-integrated silicon-monovacancy defects.
Fig. 4: Single-shot UV laser annealing.

Data availability

The data that support the findings of this work are presented in the Letter and the Supplementary Information. Source data are provided with this paper.


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We thank X. Zhang for fabrication support. This work was supported by the Science and Technology Center for Integrated Quantum Materials, NSF grant no. DMR-1231319. Portions of this work were performed at the Harvard University Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Coordinated Infrastructure Network (NNCI), which is supported by the National Science Foundation under NSF award no. ECCS-2025158. A.M.D. acknowledges funding from the Science and Technology Center for Integrated Quantum Materials, NSF grant no. DMR-1231319. J.R.D. acknowledges funding from NSF RAISE-TAQS Award 1839164. M.S. acknowledges funding from a NASA Space Technology Graduate Research Fellowship. M.Y. acknowledges funding from the Department of Defense (DoD) through the National Defense Science and Engineering Graduate (NDSEG) Fellowship Program.

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Authors and Affiliations



A.M.D., J.R.D. and E.L.H. designed the research. A.M.D. and J.R.D. performed all the measurements and data analysis, with assistance from M.S. and M.Y. All the authors contributed to preparing the manuscript.

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Correspondence to Evelyn L. Hu.

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Nature Materials thanks Marina Radulaski and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Sections I–XI, Figs. 1–16 and Table 1.

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Source Data Fig. 1

Source data for Fig. 1. The subplots are organized in separate sheets.

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Source Data Fig. 3

Source data for Fig. 3. The subplots are organized in separate sheets.

Source Data Fig. 4

Source data for Fig. 4. The subplots are organized in separate sheets.

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Day, A.M., Dietz, J.R., Sutula, M. et al. Laser writing of spin defects in nanophotonic cavities. Nat. Mater. 22, 696–702 (2023).

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