Abstract
Surface plasmon polaritons and phonon polaritons offer a means of surpassing the diffraction limit of conventional optics and facilitate efficient energy storage, local field enhancement and highsensitivity sensing, benefiting from their subwavelength confinement of light. Unfortunately, losses severely limit the propagation decay length, thus restricting the practical use of polaritons. While optimizing the fabrication technique can help circumvent the scattering loss of imperfect structures, the intrinsic absorption channel leading to heat production cannot be eliminated. Here, we utilize synthetic optical excitation of complex frequency with virtual gain, synthesized by combining the measurements made at multiple real frequencies, to compensate losses in the propagations of phonon polaritons with dramatically enhanced propagation distance. The concept of synthetic complex frequency excitation represents a viable solution to the loss problem for various applications including photonic circuits, waveguiding and plasmonic/phononic structured illumination microscopy.
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Data availability
The data that support the findings of this study are available within this Article and the Supplementary Information.
Code availability
The code that supports the findings of this study is available from the corresponding author upon reasonable request.
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Acknowledgements
This work was supported by New Cornerstone Science Foundation and the Research Grants Council of Hong Kong, AoE/P-701/20, 17315522, A-HKU705/21 (to Shuang Zhang), the National Natural Science Foundation of China (51925203 to Q.D.; 52022025 to X.Y. and 52102160 to X.G.) and the Young Elite Scientists Sponsorship Program by CAST, 2022QNRC001 (to X.G.).
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Shuang Zhang, F.G., Q.D. and X.G. conceived the project. F.G. and X.G. designed the experiments. X.G. and Shu Zhang prepared the experimental samples and performed the s-SNOM experiments with the help of C.W.; F.G. and X.G. analysed the experimental data and performed the simulation. F.G., X.G., Shu Zhang, K.Z., Y.H., Y.X., S. Zhou, X.Y., Q.D. and Shuang Zhang participated in the analysis of the results. F.G., X.G. and Shuang Zhang wrote the manuscript with input from all authors. Shuang Zhang and Q.D. supervised the overall projects. All authors contributed to the discussion.
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Supplementary Sections 1–4 and Figs. 1–11.
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Guan, F., Guo, X., Zhang, S. et al. Compensating losses in polariton propagation with synthesized complex frequency excitation. Nat. Mater. 23, 506–511 (2024). https://doi.org/10.1038/s41563-023-01787-8
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DOI: https://doi.org/10.1038/s41563-023-01787-8
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