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An integrated broadband spectrometer on thin-film lithium niobate


Optical spectrometry is a tool to investigate wavelength-dependent light–matter interactions and is widely used in astronomy, physics and chemistry. Integration and miniaturization of the currently bulky spectrometers will have an impact on applications where compactness and low complexity are key, such as air- and spaceborne missions. A high-resolution spectroscopy principle based on the near-field detection of a spatial standing wave inside a subwavelength waveguide has shown great promise to accomplish some of the aforementioned demands. However, small-scale devices based on this principle face strong bandwidth limitations due to undersampling of the standing wave. Here, we demonstrate an integrated single-waveguide Fourier transform spectrometer with an operational bandwidth of 500 nm in the near- and short-wavelength infrared, not relying on any moving components. The prototype device, with a footprint of less than 10 mm2, exploits the electro-optic properties of thin-film lithium niobate in order to retrieve the complete spatial interferogram.

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Fig. 1: Electro-optic sampling of the broadband interferogram.
Fig. 2: Electro-optic LN waveguide spectrometer.
Fig. 3: Monochromatic and dual-wavelength measurements.
Fig. 4: Broadband spectra.

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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


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We acknowledge support for nanofabrication from the Scientific Center of Optical and Electron Microscopy ScopeM and from the cleanroom facilities BRNC and FIRST of ETH Zürich. This project was initially funded by the Swiss Space Office at the State Secretariat for Education, Research and Innovation, in the frame of the Mesures de Positionnement MdP2016 funding scheme. This project has received funding from the European Union’s Horizon 2020 research and innovation programme from the European Research Council under grant no. 714837 (Chi2-nano-oxides). This work was also supported by Swiss National Science Foundation grant no. 150609. We are also grateful to the Swiss Space Center for thoughtful inputs during the project progress review meetings. We thank I. Shorubalko for contributing to the prototype preparation and G. Scalari and J. Faist for helpful discussions.

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Authors and Affiliations



B.G. and M.M. developed the original idea of directly combining electro-optic actuators with the waveguide spectrometers to carry out integrated interferogram scanning. M.M., A.S., U.M., E.A. and R.G. conceived the project. D.P., M.R.E., F.K. and A.S. developed the fabrication process. D.P., M.R.E., M.M., F.K., P.B. and A.S. designed the set-up and performed the experiments. P.G. and B.G. provided technical advice in the course of the project. D.P., M.R.E. and R.G. wrote the manuscript. M.M. and R.G. supervised the project. U.M. managed the administrative and financial aspects of the project.

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Correspondence to David Pohl.

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Pohl, D., Reig Escalé, M., Madi, M. et al. An integrated broadband spectrometer on thin-film lithium niobate. Nat. Photonics 14, 24–29 (2020).

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