Optical Imaging and Absolute Absorption Cross Section Measurement of Individual Nano-objects on Opaque Substrates:...

Optical detection of an individual single nano-object on an opaque substrate and direct determination of its absorption cross section is demonstrated using reflective spatial modulation spectroscopy. This method is applied to optical imaging and investigation of individual single-wall carbon nanotubes in the 1.6 nm diameter range on silicon substrates, which are also individually characterized by atomic force microscopy, scanning electron microscopy, and in situ micro-Raman spectroscopy. Absorption cross sections on the order of 10^-17 cm² per carbon atom are measured for the investigated semiconducting carbon nanotubes, with a light polarization absorption anisotropy of about 2.