Non-Hermitian wave engineering has attracted a surge of interest in photonics in recent years. Prominent non-Hermitian phenomena include coherent perfect absorption and its generalization, reflectionless scattering modes, in which electromagnetic scattering at the input ports is suppressed due to critical coupling with the power leaked to output ports, and interference phenomena. These concepts are ideally suited to enable real-time dynamic control over absorption, scattering and radiation. Nonetheless, reflectionless scattering modes have not been observed in complex photonic platforms involving open systems and multiple inputs. Here we demonstrate the emergence of reflectionless scattering modes in a chaotic photonic microcavity involving over a thousand optical modes. We model the optical fields in a silicon stadium microcavity within a quasi-normal mode expansion, which is able to capture a dense family of reflection zeros at the input ports, associated with reflectionless scattering modes. We observe non-Hermitian degeneracies of reflectionless scattering modes in the telecommunication wavelength band, enabling efficient dynamic control over light radiation from the cavity.
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Source data are provided with this paper. All other data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
The codes and the in-house software used in this work are available upon request to the corresponding authors.
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We thank Z. Li at Stevens Institute of Technology for polishing the edge couplers. This work was supported by the Air Force Office of Scientific Research and the Simons Foundation. Fabrication of samples for this work was performed at the Nanofabrication Facility at the Advanced Science Research Center at The Graduate Center of the City University of New York.
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b, Eigenfrequencies across Re(kR) = 25.0–29.2. c, Mode contributions from 47 notable quasi-normal modes. d, Magnitudes of the eigenvalues of the truncated scattering matrix. e, Complex reflection zeros across Re(kR) = 25.0–29.2.
a, Reflectance across 1,520–1,545 nm for different relative phases. b–c, Reflectance at RSM(±) for different relative phases. d,g, Two-dimensional data of Husimi plots.
Radiated power at different relative phases.
a, Reflectance at RSM degeneracy for different relative phases. b, Radiated power at different relative phases at RSM degeneracy. d, Radiated power at different relative phases at different angles at RSM degeneracy.
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Jiang, X., Yin, S., Li, H. et al. Coherent control of chaotic optical microcavity with reflectionless scattering modes. Nat. Phys. (2023). https://doi.org/10.1038/s41567-023-02242-w
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