Apertureless scanning near-field optical microscopy: a comparison between homodyne and heterodyne approaches. - Gomez, Lewis; Bachelot, Renaud; Bouhelier, Alexandre; Wiederrecht, Gary P.; Shih-hui Chang; Gray, Stephen K.; Feng Hua; Seokwoo Jeon; Rogers, John A.; Castro, Miguel E.; Blaize, Sylvain; Stefanon, Ilan; et al. (Journal of the Optical Society of America. B, Optical Physics, 2006)