With this erratum we aim to correct the errors that unfortunately appeared in our previous paper: In Eq. (1) number 2 is missing in the denominator, Eq. (2) and Eq. (4) are corrected consequently. All methods, calculations and conclusions are unchanged.
© 2014 Optical Society of America
OSA participates in Crossref's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.
Alert me when this article is cited.
Equations on this page are rendered with MathJax. Learn more.