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A wavelength-scale black phosphorus spectrometer


On-chip spectrometers with compact footprints are being extensively investigated owing to their promising future in critical applications such as sensing, surveillance and spectral imaging. Most existing miniaturized spectrometers use large arrays of photodetection elements to capture different spectral components of incident light, from which its spectrum is reconstructed. Here, we demonstrate a mid-infrared spectrometer in the 2–9 µm spectral range, utilizing a single tunable black phosphorus photodetector with an active area footprint of only 9 × 16 µm2, along with a unique spectral learning procedure. Such a single-detector spectrometer has a compact size at the scale of the operational wavelength. Leveraging the wavelength and bias-dependent responsivity matrix learned from the spectra of a tunable blackbody source, we reconstruct unknown spectra from their corresponding photoresponse vectors. Enabled by the strong Stark effect and the tunable light–matter interactions in black phosphorus, our single-detector spectrometer shows remarkable potential in the reconstruction of the spectra of both monochromatic and broadband light. Furthermore, its ultracompact structure that is free from bulky interferometers and gratings, together with its electrically reconfigurable nature, may open up pathways towards on-chip mid-infrared spectroscopy and spectral imaging.

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Fig. 1: The operational principle of the single-detector BP spectrometer consists of three steps: learning, sampling and reconstruction.
Fig. 2: Characterization of the tunable BP spectrometer.
Fig. 3: Spectral responsivity matrix learning.
Fig. 4: Spectroscopy demonstrations.

Data availability

The data that support the plots within this paper are available from the corresponding author upon reasonable request.

Code availability

The code and algorithm in this paper are available from the corresponding author upon reasonable request.


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F.X. and S.Y. acknowledge financial support by the Israel Ministry of Defense. The measurements at Yale also leveraged some instruments acquired through the Air Force Office of Scientific Research (AFOSR) Defense University Research Instrumentation Program (DURIP) with contract number FA9550-19-1-0109. D.N. would like to thank the Israel Science Foundation (grant number 1055/15) and the Directorate of Defense Research and Development at the Israel Ministry of Defense for the generous support of this research. Growth of hexagonal boron nitride crystals by K.W. and T.T. was supported by the Elemental Strategy Initiative conducted by the Japan Ministry of Education, Culture, Sports, Science and Technology (MEXT; grant number JPMXP0112101001), the Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (JSPS KAKENHI; grant number JP20H00354) and the Japan Science and Technology Agency Core Research for Evolutional Science and Technology (CREST; grant number JPMJCR15F3). We also thank C. Chen, A. Levi, R. Snitkoff, O. Nager, B. Deng and C. Ma, and our previous group member X. Chen for their help and support.

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Authors and Affiliations



S.Y., D.N. and F.X. conceived the idea and initiated the project. S.Y. performed the experiments, collected all the data and developed the analysing computer programs. K.W. and T.T. synthesized the hBN crystals. All the authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Fengnian Xia.

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Competing interests

S.Y., D.N. and F.X. are applying for an international patent based on the spectroscopy scheme and results presented in this work. The remaining authors declare no competing interests.

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Peer review information Nature Photonics thanks the anonymous reviewers for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1 and 2 and Table 1.

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Yuan, S., Naveh, D., Watanabe, K. et al. A wavelength-scale black phosphorus spectrometer. Nat. Photon. 15, 601–607 (2021).

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