In the Research Highlight 'Integrated isolators' (Nature Photon. 5, 571; 2011), a silicon waveguide system was reported as being able to function as an optical isolator. A technical comment recently published (Science 335, 38b–38c; 2012) has now clarified that the waveguide structure is in fact Lorentz reciprocal and cannot function in this manner as it exhibits a symmetric scattering matrix.

This Research Highlight has now been removed from the Nature Photonics website.