Correction to: Nature Photonics https://doi.org/10.1038/nphoton.2011.168, published online 7 August 2011.

In the version of Article originally published, a graphical handling error occurred, leading to the y-axis values and tick placement from Fig. 2a being duplicated in Fig. 2b. The correct panel b y-axis, ranging from 100 – 103 (rather than 10–1 – 103) is shown below.

Fig. 2
figure 1

Corrected.