Abstract
Spectral imaging is a critical technology for analysing the spectral and spatial information of input light signals for both scientific research and industrial uses. Traditional imaging systems, typically incorporating spectrometers with bulky optical components and moving mechanical parts, hinder miniaturization and on-chip integration, which is crucial for in situ spectroscopy and high-speed spectral imaging. This challenge has driven efforts towards highly integrated imaging devices and small-footprint spectrometers, aiming for portable and integrable spectral imagers. Here, inspired by the success of the digital camera-on-a-chip device concept, we develop a miniaturized on-chip spectral imager design based on a vertically cascaded n–p–n photodiode array. The device incorporates an AlGaN-based n–p diode with a compositionally graded profile in the active region in conjunction with a GaN-based p–n diode. Our proof-of-concept configuration enables electrically tunable spectral measurements from 250 nm to 365 nm, a spectral range previously inaccessible to miniaturized on-chip spectral imagers. The device achieves a high peak wavelength accuracy of 0.62 nm and a sub-10-ns response time. We demonstrate a 10 × 10 cascaded diode array for direct spectral imaging with high-quality spectral-to-spatial mapping. We spatially distinguish thin films of four organic materials on the same substrate through single-shot imaging. Our work establishes a scalable pathway for manufacturing and integrating spectral imagers into portable systems at low cost.
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Data availability
All the data needed to evaluate the conclusions in the paper are presented in the paper and/or Supplementary Information. Additional data related to this paper are available from the corresponding author upon reasonable request. Source data are provided with this paper.
Code availability
The codes that support the findings of this study are available from the corresponding author upon reasonable request.
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Acknowledgements
This work was funded by the National Natural Science Foundation of China (grant nos. 62322410 to H.S. and T252790007 to S.L.), the National Key Research & Development Program of China (grant no. 2023YFB3610500 to H.S.), the Anhui Provincial Natural Science Foundation (grant no. 2308085J08 to H.S.) and the National Key Research and Development Program of China (grant no. 2023YFB3405600 to Z.Y.). This work was partially conducted at the Center for Micro- and Nanoscale Research and Fabrication, as well as at the Instruments Center for Physical Science at the University of Science and Technology of China.
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H.S. conceived of the ideas during discussions with H.Y. and designed the experiments. H.Y. and M.H.M. carried out the characterizations and measurements. H.Y., M.H.M., Z.G., Y.L., Y.K. and Q.Z. grew the cascaded photodiode heterostructures and fabricated the devices. M.Y., Y.C. and Z.Y. developed the reconstruction code. H.Y., M.H.M., Z.G., Y.L., Y.K., Q.Z. and W.C. analysed the data. S.L., Z.Y. and T.H. commented on the experimental results and helped with the data analysis. H.Y. and H.S. wrote the paper, and H.S. supervised the research. All the authors participated in the scientific discussion extensively and contributed to the writing of the paper.
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H.S. and H.Y. have filed a Chinese patent application (202510493026.2) and a patent cooperation treaty (PCT) patent application (PCT/CN2025/089863) related to the framework presented in this work. The other authors declare no competing interests.
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Yu, H., Memon, M.H., Yao, M. et al. A miniaturized cascaded-diode-array spectral imager. Nat. Photon. (2025). https://doi.org/10.1038/s41566-025-01754-6
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DOI: https://doi.org/10.1038/s41566-025-01754-6
