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  • Letter
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Subwavelength angle-sensing photodetectors inspired by directional hearing in small animals

An Author Correction to this article was published on 15 November 2018

This article has been updated


Sensing the direction of sounds gives animals clear evolutionary advantage. For large animals, with an ear-to-ear spacing that exceeds audible sound wavelengths, directional sensing is simply accomplished by recognizing the intensity and time differences of a wave impinging on its two ears1. Recent research suggests that in smaller, subwavelength animals, angle sensing can instead rely on a coherent coupling of soundwaves between the two ears2,3,4. Inspired by this natural design, here we show a subwarvelength photodetection pixel that can measure both the intensity and incident angle of light. It relies on an electrical isolation and optical coupling of two closely spaced Si nanowires that support optical Mie resonances5,6,7. When these resonators scatter light into the same free-space optical modes, a non-Hermitian coupling results that affords highly sensitive angle determination. By straightforward photocurrent measurements, we can independently quantify the stored optical energy in each nanowire and relate the difference in the stored energy between the wires to the incident angle of a light wave. We exploit this effect to fabricate a subwavelength angle-sensitive pixel with angular sensitivity, δθ= 0.32°.

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Fig. 1: Angle sensing in optics using a lens and the internally coupled ears of a small animal.


Fig. 2: Coupled mode theory for a pair of optical Mie resonators used for directional sensing.
Fig. 3: Absorption profiles for a coupled and uncoupled pair of Si nanowires for different incident angles.
Fig. 4: Fabrication and performance of the proposed angle-sensing photodetector.
Fig. 5: Measurement set-up and experimental results for lens-less positioning.

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  • 15 November 2018

    In the version of this Letter originally published, Zongfu Yu was mistakenly not noted as being a corresponding author; this has now been corrected in all versions of the Letter.


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The work at the University of Wisconsin was funded by the Office of Naval Research (N00014-14-1-0300). The work at Stanford was supported by a Multi University Research Initiative (MURIs FA9550-14-1-0389) and an individual investigator grant (FA9550-17-1-0331) from the AFOSR.

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Authors and Affiliations



M.B. and Z.Y. directed the research. S.Y., M.Z., P.F. and D.L. performed the experiments. S.Y. and K.X.W. performed the simulations. M.Z. developed the analytical theory. All authors were involved in analysing the data and writing the manuscript.

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Correspondence to Mark Brongersma.

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The authors declare no competing interests.

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Supplementary Information

Supplementary Sections 1–16; Supplementary Figs. 1–24

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Yi, S., Zhou, M., Yu, Z. et al. Subwavelength angle-sensing photodetectors inspired by directional hearing in small animals. Nature Nanotech 13, 1143–1147 (2018).

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