Correction to: Nature Photonics https://doi.org/10.1038/s41566-018-0109-4, published online 26 February 2018.

In the version of this Article originally published, in Fig. 1a, the equation ‘\({\tilde{{U}}}_{i}\left({\bf{x}};\omega ,{{\bf{k}}}_{i}\right)\)’ was missing and in equation ‘Γ(x) = iF(x) × H(x)’, the multiplication sign ‘×’ should have been the convolution operator ‘’; in the Acknowledgments, grant number ‘686271’ should have read ‘686271/SEFRI 16.0047’. These errors have now been corrected online.